# libATA Developer's Guide

Jeff
Garzik
2003-2006
Jeff Garzik

The contents of this file are subject to the Open Software License version 1.1 that can be found at http://fedoraproject.org/wiki/Licensing:OSL1.1 and is included herein by reference.

Alternatively, the contents of this file may be used under the terms of the GNU General Public License version 2 (the "GPL") as distributed in the kernel source COPYING file, in which case the provisions of the GPL are applicable instead of the above. If you wish to allow the use of your version of this file only under the terms of the GPL and not to allow others to use your version of this file under the OSL, indicate your decision by deleting the provisions above and replace them with the notice and other provisions required by the GPL. If you do not delete the provisions above, a recipient may use your version of this file under either the OSL or the GPL.

## Introduction

libATA is a library used inside the Linux kernel to support ATA host controllers and devices. libATA provides an ATA driver API, class transports for ATA and ATAPI devices, and SCSI<->ATA translation for ATA devices according to the T10 SAT specification.

This Guide documents the libATA driver API, library functions, library internals, and a couple sample ATA low-level drivers.

## libata Driver API

struct ata_port_operations is defined for every low-level libata hardware driver, and it controls how the low-level driver interfaces with the ATA and SCSI layers.

FIS-based drivers will hook into the system with ->qc_prep() and ->qc_issue() high-level hooks. Hardware which behaves in a manner similar to PCI IDE hardware may utilize several generic helpers, defining at a bare minimum the bus I/O addresses of the ATA shadow register blocks.

### struct ata_port_operations

#### Disable ATA port

    void (*port_disable) (struct ata_port *);

Called from ata_bus_probe() error path, as well as when unregistering from the SCSI module (rmmod, hot unplug). This function should do whatever needs to be done to take the port out of use. In most cases, ata_port_disable() can be used as this hook.

Called from ata_bus_probe() on a failed probe. Called from ata_scsi_release().

#### Post-IDENTIFY device configuration

    void (*dev_config) (struct ata_port *, struct ata_device *);

Called after IDENTIFY [PACKET] DEVICE is issued to each device found. Typically used to apply device-specific fixups prior to issue of SET FEATURES - XFER MODE, and prior to operation.

This entry may be specified as NULL in ata_port_operations.

#### Set PIO/DMA mode

    void (*set_piomode) (struct ata_port *, struct ata_device *);
    void (*set_dmamode) (struct ata_port *, struct ata_device *);
    void (*post_set_mode) (struct ata_port *);
    unsigned int (*mode_filter) (struct ata_port *, struct ata_device *, unsigned int);

Hooks called prior to the issue of SET FEATURES - XFER MODE command. The optional ->mode_filter() hook is called when libata has built a mask of the possible modes. This is passed to the ->mode_filter() function which should return a mask of valid modes after filtering those unsuitable due to hardware limits. It is not valid to use this interface to add modes.

dev->pio_mode and dev->dma_mode are guaranteed to be valid when ->set_piomode() and when ->set_dmamode() is called. The timings for any other drive sharing the cable will also be valid at this point. That is the library records the decisions for the modes of each drive on a channel before it attempts to set any of them.

->post_set_mode() is called unconditionally, after the SET FEATURES - XFER MODE command completes successfully.

->set_piomode() is always called (if present), but ->set_dma_mode() is only called if DMA is possible.

#### Taskfile read/write

    void (*sff_tf_load) (struct ata_port *ap, struct ata_taskfile *tf);
    void (*sff_tf_read) (struct ata_port *ap, struct ata_taskfile *tf);

->tf_load() is called to load the given taskfile into hardware registers / DMA buffers. ->tf_read() is called to read the hardware registers / DMA buffers, to obtain the current set of taskfile register values. Most drivers for taskfile-based hardware (PIO or MMIO) use ata_sff_tf_load() and ata_sff_tf_read() for these hooks.

#### PIO data read/write

    void (*sff_data_xfer) (struct ata_device *, unsigned char *, unsigned int, int);

All bmdma-style drivers must implement this hook. This is the low-level operation that actually copies the data bytes during a PIO data transfer. Typically the driver will choose one of ata_sff_data_xfer_noirq(), ata_sff_data_xfer(), or ata_sff_data_xfer32().

#### ATA command execute

    void (*sff_exec_command)(struct ata_port *ap, struct ata_taskfile *tf);

causes an ATA command, previously loaded with ->tf_load(), to be initiated in hardware. Most drivers for taskfile-based hardware use ata_sff_exec_command() for this hook.

#### Per-cmd ATAPI DMA capabilities filter

    int (*check_atapi_dma) (struct ata_queued_cmd *qc);

Allow low-level driver to filter ATA PACKET commands, returning a status indicating whether or not it is OK to use DMA for the supplied PACKET command.

This hook may be specified as NULL, in which case libata will assume that atapi dma can be supported.

#### Read specific ATA shadow registers

    u8   (*sff_check_status)(struct ata_port *ap);
    u8   (*sff_check_altstatus)(struct ata_port *ap);

Reads the Status/AltStatus ATA shadow register from hardware. On some hardware, reading the Status register has the side effect of clearing the interrupt condition. Most drivers for taskfile-based hardware use ata_sff_check_status() for this hook.

#### Write specific ATA shadow register

    void (*sff_set_devctl)(struct ata_port *ap, u8 ctl);

Write the device control ATA shadow register to the hardware. Most drivers don't need to define this.

#### Select ATA device on bus

    void (*sff_dev_select)(struct ata_port *ap, unsigned int device);

Issues the low-level hardware command(s) that causes one of N hardware devices to be considered 'selected' (active and available for use) on the ATA bus. This generally has no meaning on FIS-based devices.

Most drivers for taskfile-based hardware use ata_sff_dev_select() for this hook.

#### Private tuning method

    void (*set_mode) (struct ata_port *ap);

By default libata performs drive and controller tuning in accordance with the ATA timing rules and also applies blacklists and cable limits. Some controllers need special handling and have custom tuning rules, typically raid controllers that use ATA commands but do not actually do drive timing.

This hook should not be used to replace the standard controller tuning logic when a controller has quirks. Replacing the default tuning logic in that case would bypass handling for drive and bridge quirks that may be important to data reliability. If a controller needs to filter the mode selection it should use the mode_filter hook instead.

#### Control PCI IDE BMDMA engine

    void (*bmdma_setup) (struct ata_queued_cmd *qc);
    void (*bmdma_start) (struct ata_queued_cmd *qc);
    void (*bmdma_stop) (struct ata_port *ap);
    u8   (*bmdma_status) (struct ata_port *ap);

When setting up an IDE BMDMA transaction, these hooks arm (->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop) the hardware's DMA engine. ->bmdma_status is used to read the standard PCI IDE DMA Status register.

These hooks are typically either no-ops, or simply not implemented, in FIS-based drivers.

Most legacy IDE drivers use ata_bmdma_setup() for the bmdma_setup() hook. ata_bmdma_setup() will write the pointer to the PRD table to the IDE PRD Table Address register, enable DMA in the DMA Command register, and call exec_command() to begin the transfer.

Most legacy IDE drivers use ata_bmdma_start() for the bmdma_start() hook. ata_bmdma_start() will write the ATA_DMA_START flag to the DMA Command register.

Many legacy IDE drivers use ata_bmdma_stop() for the bmdma_stop() hook. ata_bmdma_stop() clears the ATA_DMA_START flag in the DMA command register.

Many legacy IDE drivers use ata_bmdma_status() as the bmdma_status() hook.

#### High-level taskfile hooks

    void (*qc_prep) (struct ata_queued_cmd *qc);
    int (*qc_issue) (struct ata_queued_cmd *qc);

Higher-level hooks, these two hooks can potentially supercede several of the above taskfile/DMA engine hooks. ->qc_prep is called after the buffers have been DMA-mapped, and is typically used to populate the hardware's DMA scatter-gather table. Most drivers use the standard ata_qc_prep() helper function, but more advanced drivers roll their own.

->qc_issue is used to make a command active, once the hardware and S/G tables have been prepared. IDE BMDMA drivers use the helper function ata_qc_issue_prot() for taskfile protocol-based dispatch. More advanced drivers implement their own ->qc_issue.

ata_qc_issue_prot() calls ->tf_load(), ->bmdma_setup(), and ->bmdma_start() as necessary to initiate a transfer.

#### Exception and probe handling (EH)

    void (*eng_timeout) (struct ata_port *ap);
    void (*phy_reset) (struct ata_port *ap);

Deprecated. Use ->error_handler() instead.

    void (*freeze) (struct ata_port *ap);
    void (*thaw) (struct ata_port *ap);

ata_port_freeze() is called when HSM violations or some other condition disrupts normal operation of the port. A frozen port is not allowed to perform any operation until the port is thawed, which usually follows a successful reset.

The optional ->freeze() callback can be used for freezing the port hardware-wise (e.g. mask interrupt and stop DMA engine). If a port cannot be frozen hardware-wise, the interrupt handler must ack and clear interrupts unconditionally while the port is frozen.

The optional ->thaw() callback is called to perform the opposite of ->freeze(): prepare the port for normal operation once again. Unmask interrupts, start DMA engine, etc.

    void (*error_handler) (struct ata_port *ap);

->error_handler() is a driver's hook into probe, hotplug, and recovery and other exceptional conditions. The primary responsibility of an implementation is to call ata_do_eh() or ata_bmdma_drive_eh() with a set of EH hooks as arguments:

'prereset' hook (may be NULL) is called during an EH reset, before any other actions are taken.

'postreset' hook (may be NULL) is called after the EH reset is performed. Based on existing conditions, severity of the problem, and hardware capabilities,

Either 'softreset' (may be NULL) or 'hardreset' (may be NULL) will be called to perform the low-level EH reset.

    void (*post_internal_cmd) (struct ata_queued_cmd *qc);

Perform any hardware-specific actions necessary to finish processing after executing a probe-time or EH-time command via ata_exec_internal().

#### Hardware interrupt handling

    irqreturn_t (*irq_handler)(int, void *, struct pt_regs *);
    void (*irq_clear) (struct ata_port *);

->irq_handler is the interrupt handling routine registered with the system, by libata. ->irq_clear is called during probe just before the interrupt handler is registered, to be sure hardware is quiet.

The second argument, dev_instance, should be cast to a pointer to struct ata_host_set.

Most legacy IDE drivers use ata_sff_interrupt() for the irq_handler hook, which scans all ports in the host_set, determines which queued command was active (if any), and calls ata_sff_host_intr(ap,qc).

Most legacy IDE drivers use ata_sff_irq_clear() for the irq_clear() hook, which simply clears the interrupt and error flags in the DMA status register.

#### SATA phy read/write

    int (*scr_read) (struct ata_port *ap, unsigned int sc_reg,
    		 u32 *val);
    int (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
                       u32 val);

Read and write standard SATA phy registers. Currently only used if ->phy_reset hook called the sata_phy_reset() helper function. sc_reg is one of SCR_STATUS, SCR_CONTROL, SCR_ERROR, or SCR_ACTIVE.

#### Init and shutdown

    int (*port_start) (struct ata_port *ap);
    void (*port_stop) (struct ata_port *ap);
    void (*host_stop) (struct ata_host_set *host_set);

->port_start() is called just after the data structures for each port are initialized. Typically this is used to alloc per-port DMA buffers / tables / rings, enable DMA engines, and similar tasks. Some drivers also use this entry point as a chance to allocate driver-private memory for ap->private_data.

Many drivers use ata_port_start() as this hook or call it from their own port_start() hooks. ata_port_start() allocates space for a legacy IDE PRD table and returns.

->port_stop() is called after ->host_stop(). Its sole function is to release DMA/memory resources, now that they are no longer actively being used. Many drivers also free driver-private data from port at this time.

->host_stop() is called after all ->port_stop() calls have completed. The hook must finalize hardware shutdown, release DMA and other resources, etc. This hook may be specified as NULL, in which case it is not called.

## Error handling

This chapter describes how errors are handled under libata. Readers are advised to read SCSI EH (Documentation/scsi/scsi_eh.txt) and ATA exceptions doc first.

### Origins of commands

In libata, a command is represented with struct ata_queued_cmd or qc. qc's are preallocated during port initialization and repetitively used for command executions. Currently only one qc is allocated per port but yet-to-be-merged NCQ branch allocates one for each tag and maps each qc to NCQ tag 1-to-1.

libata commands can originate from two sources - libata itself and SCSI midlayer. libata internal commands are used for initialization and error handling. All normal blk requests and commands for SCSI emulation are passed as SCSI commands through queuecommand callback of SCSI host template.

### How commands are issued

Internal commands

  First, qc is allocated and initialized using ata_qc_new_init(). Although ata_qc_new_init() doesn't implement any wait or retry mechanism when qc is not available, internal commands are currently issued only during initialization and error recovery, so no other command is active and allocation is guaranteed to succeed.

  Once allocated qc's taskfile is initialized for the command to be executed. qc currently has two mechanisms to notify completion. One is via qc->complete_fn() callback and the other is completion qc->waiting. qc->complete_fn() callback is the asynchronous path used by normal SCSI translated commands and qc->waiting is the synchronous (issuer sleeps in process context) path used by internal commands.

  Once initialization is complete, host_set lock is acquired and the qc is issued.

SCSI commands

  All libata drivers use ata_scsi_queuecmd() as hostt->queuecommand callback. scmds can either be simulated or translated. No qc is involved in processing a simulated scmd. The result is computed right away and the scmd is completed.

  For a translated scmd, ata_qc_new_init() is invoked to allocate a qc and the scmd is translated into the qc. SCSI midlayer's completion notification function pointer is stored into qc->scsidone.

  qc->complete_fn() callback is used for completion notification. ATA commands use ata_scsi_qc_complete() while ATAPI commands use atapi_qc_complete(). Both functions end up calling qc->scsidone to notify upper layer when the qc is finished. After translation is completed, the qc is issued with ata_qc_issue().

  Note that SCSI midlayer invokes hostt->queuecommand while holding host_set lock, so all above occur while holding host_set lock.

### How commands are processed

Depending on which protocol and which controller are used, commands are processed differently. For the purpose of discussion, a controller which uses taskfile interface and all standard callbacks is assumed.

Currently 6 ATA command protocols are used. They can be sorted into the following four categories according to how they are processed.

ATA NO DATA or DMA

  ATA_PROT_NODATA and ATA_PROT_DMA fall into this category. These types of commands don't require any software intervention once issued. Device will raise interrupt on completion.

ATA PIO

  ATA_PROT_PIO is in this category. libata currently implements PIO with polling. ATA_NIEN bit is set to turn off interrupt and pio_task on ata_wq performs polling and IO.

ATAPI NODATA or DMA

  ATA_PROT_ATAPI_NODATA and ATA_PROT_ATAPI_DMA are in this category. packet_task is used to poll BSY bit after issuing PACKET command. Once BSY is turned off by the device, packet_task transfers CDB and hands off processing to interrupt handler.

ATAPI PIO

  ATA_PROT_ATAPI is in this category. ATA_NIEN bit is set and, as in ATAPI NODATA or DMA, packet_task submits cdb. However, after submitting cdb, further processing (data transfer) is handed off to pio_task.

### How commands are completed

Once issued, all qc's are either completed with ata_qc_complete() or time out. For commands which are handled by interrupts, ata_host_intr() invokes ata_qc_complete(), and, for PIO tasks, pio_task invokes ata_qc_complete(). In error cases, packet_task may also complete commands.

ata_qc_complete() does the following.

1. DMA memory is unmapped.

2. ATA_QCFLAG_ACTIVE is clared from qc->flags.

3. qc->complete_fn() callback is invoked. If the return value of the callback is not zero. Completion is short circuited and ata_qc_complete() returns.

4. __ata_qc_complete() is called, which does

   1. qc->flags is cleared to zero.

   2. ap->active_tag and qc->tag are poisoned.

   3. qc->waiting is claread & completed (in that order).

   4. qc is deallocated by clearing appropriate bit in ap->qactive.

So, it basically notifies upper layer and deallocates qc. One exception is short-circuit path in #3 which is used by atapi_qc_complete().

For all non-ATAPI commands, whether it fails or not, almost the same code path is taken and very little error handling takes place. A qc is completed with success status if it succeeded, with failed status otherwise.

However, failed ATAPI commands require more handling as REQUEST SENSE is needed to acquire sense data. If an ATAPI command fails, ata_qc_complete() is invoked with error status, which in turn invokes atapi_qc_complete() via qc->complete_fn() callback.

This makes atapi_qc_complete() set scmd->result to SAM_STAT_CHECK_CONDITION, complete the scmd and return 1. As the sense data is empty but scmd->result is CHECK CONDITION, SCSI midlayer will invoke EH for the scmd, and returning 1 makes ata_qc_complete() to return without deallocating the qc. This leads us to ata_scsi_error() with partially completed qc.

### ata_scsi_error()

ata_scsi_error() is the current transportt->eh_strategy_handler() for libata. As discussed above, this will be entered in two cases - timeout and ATAPI error completion. This function calls low level libata driver's eng_timeout() callback, the standard callback for which is ata_eng_timeout(). It checks if a qc is active and calls ata_qc_timeout() on the qc if so. Actual error handling occurs in ata_qc_timeout().

If EH is invoked for timeout, ata_qc_timeout() stops BMDMA and completes the qc. Note that as we're currently in EH, we cannot call scsi_done. As described in SCSI EH doc, a recovered scmd should be either retried with scsi_queue_insert() or finished with scsi_finish_command(). Here, we override qc->scsidone with scsi_finish_command() and calls ata_qc_complete().

If EH is invoked due to a failed ATAPI qc, the qc here is completed but not deallocated. The purpose of this half-completion is to use the qc as place holder to make EH code reach this place. This is a bit hackish, but it works.

Once control reaches here, the qc is deallocated by invoking __ata_qc_complete() explicitly. Then, internal qc for REQUEST SENSE is issued. Once sense data is acquired, scmd is finished by directly invoking scsi_finish_command() on the scmd. Note that as we already have completed and deallocated the qc which was associated with the scmd, we don't need to/cannot call ata_qc_complete() again.

### Problems with the current EH

- Error representation is too crude. Currently any and all error conditions are represented with ATA STATUS and ERROR registers. Errors which aren't ATA device errors are treated as ATA device errors by setting ATA_ERR bit. Better error descriptor which can properly represent ATA and other errors/exceptions is needed.

- When handling timeouts, no action is taken to make device forget about the timed out command and ready for new commands.

- EH handling via ata_scsi_error() is not properly protected from usual command processing. On EH entrance, the device is not in quiescent state. Timed out commands may succeed or fail any time. pio_task and atapi_task may still be running.

- Too weak error recovery. Devices / controllers causing HSM mismatch errors and other errors quite often require reset to return to known state. Also, advanced error handling is necessary to support features like NCQ and hotplug.

- ATA errors are directly handled in the interrupt handler and PIO errors in pio_task. This is problematic for advanced error handling for the following reasons.

  First, advanced error handling often requires context and internal qc execution.

  Second, even a simple failure (say, CRC error) needs information gathering and could trigger complex error handling (say, resetting & reconfiguring). Having multiple code paths to gather information, enter EH and trigger actions makes life painful.

  Third, scattered EH code makes implementing low level drivers difficult. Low level drivers override libata callbacks. If EH is scattered over several places, each affected callbacks should perform its part of error handling. This can be error prone and painful.

## libata Library

### LINUX

Kernel Hackers Manual August 2015
ata_link_next
9
3.13.0-63-

### ata_link_next

link iteration helper

#### Synopsis

       struct ata_link * ata_link_next
       struct ata_link * link
       struct ata_port * ap
       enum ata_link_iter_mode mode

#### Arguments

`link`

  the previous link, NULL to start

`ap`

  ATA port containing links to iterate

`mode`

  iteration mode, one of ATA_LITER_*

#### LOCKING

Host lock or EH context.

#### RETURNS

Pointer to the next link.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_next
9
3.13.0-63-

### ata_dev_next

device iteration helper

#### Synopsis

       struct ata_device * ata_dev_next
       struct ata_device * dev
       struct ata_link * link
       enum ata_dev_iter_mode mode

#### Arguments

`dev`

  the previous device, NULL to start

`link`

  ATA link containing devices to iterate

`mode`

  iteration mode, one of ATA_DITER_*

#### LOCKING

Host lock or EH context.

#### RETURNS

Pointer to the next device.

### LINUX

Kernel Hackers Manual August 2015
atapi_cmd_type
9
3.13.0-63-

### atapi_cmd_type

Determine ATAPI command type from SCSI opcode

#### Synopsis

       int atapi_cmd_type
       u8 opcode

#### Arguments

`opcode`

  SCSI opcode

#### Description

Determine ATAPI command type from `opcode`.

#### LOCKING

None.

#### RETURNS

ATAPI_{READ|WRITE|READ_CD|PASS_THRU|MISC}

### LINUX

Kernel Hackers Manual August 2015
ata_tf_to_fis
9
3.13.0-63-

### ata_tf_to_fis

Convert ATA taskfile to SATA FIS structure

#### Synopsis

       void ata_tf_to_fis
       const struct ata_taskfile * tf
       u8 pmp
       int is_cmd
       u8 * fis

#### Arguments

`tf`

  Taskfile to convert

`pmp`

  Port multiplier port

`is_cmd`

  This FIS is for command

`fis`

  Buffer into which data will output

#### Description

Converts a standard ATA taskfile to a Serial ATA FIS structure (Register - Host to Device).

#### LOCKING

Inherited from caller.

### LINUX

Kernel Hackers Manual August 2015
ata_tf_from_fis
9
3.13.0-63-

### ata_tf_from_fis

Convert SATA FIS to ATA taskfile

#### Synopsis

       void ata_tf_from_fis
       const u8 * fis
       struct ata_taskfile * tf

#### Arguments

`fis`

  Buffer from which data will be input

`tf`

  Taskfile to output

#### Description

Converts a serial ATA FIS structure to a standard ATA taskfile.

#### LOCKING

Inherited from caller.

### LINUX

Kernel Hackers Manual August 2015
ata_pack_xfermask
9
3.13.0-63-

### ata_pack_xfermask

Pack pio, mwdma and udma masks into xfer_mask

#### Synopsis

       unsigned long ata_pack_xfermask
       unsigned long pio_mask
       unsigned long mwdma_mask
       unsigned long udma_mask

#### Arguments

`pio_mask`

  pio_mask

`mwdma_mask`

  mwdma_mask

`udma_mask`

  udma_mask

#### Description

Pack `pio_mask`, `mwdma_mask` and `udma_mask` into a single unsigned int xfer_mask.

#### LOCKING

None.

#### RETURNS

Packed xfer_mask.

### LINUX

Kernel Hackers Manual August 2015
ata_unpack_xfermask
9
3.13.0-63-

### ata_unpack_xfermask

Unpack xfer_mask into pio, mwdma and udma masks

#### Synopsis

       void ata_unpack_xfermask
       unsigned long xfer_mask
       unsigned long * pio_mask
       unsigned long * mwdma_mask
       unsigned long * udma_mask

#### Arguments

`xfer_mask`

  xfer_mask to unpack

`pio_mask`

  resulting pio_mask

`mwdma_mask`

  resulting mwdma_mask

`udma_mask`

  resulting udma_mask

#### Description

Unpack `xfer_mask` into `pio_mask`, `mwdma_mask` and `udma_mask`. Any NULL distination masks will be ignored.

### LINUX

Kernel Hackers Manual August 2015
ata_xfer_mask2mode
9
3.13.0-63-

### ata_xfer_mask2mode

Find matching XFER_* for the given xfer_mask

#### Synopsis

       u8 ata_xfer_mask2mode
       unsigned long xfer_mask

#### Arguments

`xfer_mask`

  xfer_mask of interest

#### Description

Return matching XFER_* value for `xfer_mask`. Only the highest bit of `xfer_mask` is considered.

#### LOCKING

None.

#### RETURNS

Matching XFER_* value, 0xff if no match found.

### LINUX

Kernel Hackers Manual August 2015
ata_xfer_mode2mask
9
3.13.0-63-

### ata_xfer_mode2mask

Find matching xfer_mask for XFER_*

#### Synopsis

       unsigned long ata_xfer_mode2mask
       u8 xfer_mode

#### Arguments

`xfer_mode`

  XFER_* of interest

#### Description

Return matching xfer_mask for `xfer_mode`.

#### LOCKING

None.

#### RETURNS

Matching xfer_mask, 0 if no match found.

### LINUX

Kernel Hackers Manual August 2015
ata_xfer_mode2shift
9
3.13.0-63-

### ata_xfer_mode2shift

Find matching xfer_shift for XFER_*

#### Synopsis

       int ata_xfer_mode2shift
       unsigned long xfer_mode

#### Arguments

`xfer_mode`

  XFER_* of interest

#### Description

Return matching xfer_shift for `xfer_mode`.

#### LOCKING

None.

#### RETURNS

Matching xfer_shift, -1 if no match found.

### LINUX

Kernel Hackers Manual August 2015
ata_mode_string
9
3.13.0-63-

### ata_mode_string

convert xfer_mask to string

#### Synopsis

       const char * ata_mode_string
       unsigned long xfer_mask

#### Arguments

`xfer_mask`

  mask of bits supported; only highest bit counts.

#### Description

Determine string which represents the highest speed (highest bit in `modemask`).

#### LOCKING

None.

#### RETURNS

Constant C string representing highest speed listed in `mode_mask`, or the constant C string <n/a>.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_classify
9
3.13.0-63-

### ata_dev_classify

determine device type based on ATA-spec signature

#### Synopsis

       unsigned int ata_dev_classify
       const struct ata_taskfile * tf

#### Arguments

`tf`

  ATA taskfile register set for device to be identified

#### Description

Determine from taskfile register contents whether a device is ATA or ATAPI, as per Signature and persistence section of ATA/PI spec (volume 1, sect 5.14).

#### LOCKING

None.

#### RETURNS

Device type, `ATA_DEV_ATA`, `ATA_DEV_ATAPI`, `ATA_DEV_PMP` or `ATA_DEV_UNKNOWN` the event of failure.

### LINUX

Kernel Hackers Manual August 2015
ata_id_string
9
3.13.0-63-

### ata_id_string

Convert IDENTIFY DEVICE page into string

#### Synopsis

       void ata_id_string
       const u16 * id
       unsigned char * s
       unsigned int ofs
       unsigned int len

#### Arguments

`id`

  IDENTIFY DEVICE results we will examine

`s`

  string into which data is output

`ofs`

  offset into identify device page

`len`

  length of string to return. must be an even number.

#### Description

The strings in the IDENTIFY DEVICE page are broken up into 16-bit chunks. Run through the string, and output each 8-bit chunk linearly, regardless of platform.

#### LOCKING

caller.

### LINUX

Kernel Hackers Manual August 2015
ata_id_c_string
9
3.13.0-63-

### ata_id_c_string

Convert IDENTIFY DEVICE page into C string

#### Synopsis

       void ata_id_c_string
       const u16 * id
       unsigned char * s
       unsigned int ofs
       unsigned int len

#### Arguments

`id`

  IDENTIFY DEVICE results we will examine

`s`

  string into which data is output

`ofs`

  offset into identify device page

`len`

  length of string to return. must be an odd number.

#### Description

This function is identical to ata_id_string except that it trims trailing spaces and terminates the resulting string with null. `len` must be actual maximum length (even number) + 1.

#### LOCKING

caller.

### LINUX

Kernel Hackers Manual August 2015
ata_id_xfermask
9
3.13.0-63-

### ata_id_xfermask

Compute xfermask from the given IDENTIFY data

#### Synopsis

       unsigned long ata_id_xfermask
       const u16 * id

#### Arguments

`id`

  IDENTIFY data to compute xfer mask from

#### Description

Compute the xfermask for this device. This is not as trivial as it seems if we must consider early devices correctly.

#### FIXME

pre IDE drive timing (do we care ?).

#### LOCKING

None.

#### RETURNS

Computed xfermask

### LINUX

Kernel Hackers Manual August 2015
ata_pio_need_iordy
9
3.13.0-63-

### ata_pio_need_iordy

check if iordy needed

#### Synopsis

       unsigned int ata_pio_need_iordy
       const struct ata_device * adev

#### Arguments

`adev`

  ATA device

#### Description

Check if the current speed of the device requires IORDY. Used by various controllers for chip configuration.

### LINUX

Kernel Hackers Manual August 2015
ata_do_dev_read_id
9
3.13.0-63-

### ata_do_dev_read_id

default ID read method

#### Synopsis

       unsigned int ata_do_dev_read_id
       struct ata_device * dev
       struct ata_taskfile * tf
       u16 * id

#### Arguments

`dev`

  device

`tf`

  proposed taskfile

`id`

  data buffer

#### Description

Issue the identify taskfile and hand back the buffer containing identify data. For some RAID controllers and for pre ATA devices this function is wrapped or replaced by the driver

### LINUX

Kernel Hackers Manual August 2015
ata_cable_40wire
9
3.13.0-63-

### ata_cable_40wire

return 40 wire cable type

#### Synopsis

       int ata_cable_40wire
       struct ata_port * ap

#### Arguments

`ap`

  port

#### Description

Helper method for drivers which want to hardwire 40 wire cable detection.

### LINUX

Kernel Hackers Manual August 2015
ata_cable_80wire
9
3.13.0-63-

### ata_cable_80wire

return 80 wire cable type

#### Synopsis

       int ata_cable_80wire
       struct ata_port * ap

#### Arguments

`ap`

  port

#### Description

Helper method for drivers which want to hardwire 80 wire cable detection.

### LINUX

Kernel Hackers Manual August 2015
ata_cable_unknown
9
3.13.0-63-

### ata_cable_unknown

return unknown PATA cable.

#### Synopsis

       int ata_cable_unknown
       struct ata_port * ap

#### Arguments

`ap`

  port

#### Description

Helper method for drivers which have no PATA cable detection.

### LINUX

Kernel Hackers Manual August 2015
ata_cable_ignore
9
3.13.0-63-

### ata_cable_ignore

return ignored PATA cable.

#### Synopsis

       int ata_cable_ignore
       struct ata_port * ap

#### Arguments

`ap`

  port

#### Description

Helper method for drivers which don't use cable type to limit transfer mode.

### LINUX

Kernel Hackers Manual August 2015
ata_cable_sata
9
3.13.0-63-

### ata_cable_sata

return SATA cable type

#### Synopsis

       int ata_cable_sata
       struct ata_port * ap

#### Arguments

`ap`

  port

#### Description

Helper method for drivers which have SATA cables

### LINUX

Kernel Hackers Manual August 2015
ata_dev_pair
9
3.13.0-63-

### ata_dev_pair

return other device on cable

#### Synopsis

       struct ata_device * ata_dev_pair
       struct ata_device * adev

#### Arguments

`adev`

  device

#### Description

Obtain the other device on the same cable, or if none is present NULL is returned

### LINUX

Kernel Hackers Manual August 2015
sata_set_spd
9
3.13.0-63-

### sata_set_spd

set SATA spd according to spd limit

#### Synopsis

       int sata_set_spd
       struct ata_link * link

#### Arguments

`link`

  Link to set SATA spd for

#### Description

Set SATA spd of `link` according to sata_spd_limit.

#### LOCKING

Inherited from caller.

#### RETURNS

0 if spd doesn't need to be changed, 1 if spd has been changed. Negative errno if SCR registers are inaccessible.

### LINUX

Kernel Hackers Manual August 2015
ata_timing_cycle2mode
9
3.13.0-63-

### ata_timing_cycle2mode

find xfer mode for the specified cycle duration

#### Synopsis

       u8 ata_timing_cycle2mode
       unsigned int xfer_shift
       int cycle

#### Arguments

`xfer_shift`

  ATA_SHIFT_* value for transfer type to examine.

`cycle`

  cycle duration in ns

#### Description

Return matching xfer mode for `cycle`. The returned mode is of the transfer type specified by `xfer_shift`. If `cycle` is too slow for `xfer_shift`, 0xff is returned. If `cycle` is faster than the fastest known mode, the fasted mode is returned.

#### LOCKING

None.

#### RETURNS

Matching xfer_mode, 0xff if no match found.

### LINUX

Kernel Hackers Manual August 2015
ata_do_set_mode
9
3.13.0-63-

### ata_do_set_mode

Program timings and issue SET FEATURES - XFER

#### Synopsis

       int ata_do_set_mode
       struct ata_link * link
       struct ata_device ** r_failed_dev

#### Arguments

`link`

  link on which timings will be programmed

`r_failed_dev`

  out parameter for failed device

#### Description

Standard implementation of the function used to tune and set ATA device disk transfer mode (PIO3, UDMA6, etc.). If `ata_dev_set_mode` fails, pointer to the failing device is returned in `r_failed_dev`.

#### LOCKING

PCI/etc. bus probe sem.

#### RETURNS

0 on success, negative errno otherwise

### LINUX

Kernel Hackers Manual August 2015
ata_wait_after_reset
9
3.13.0-63-

### ata_wait_after_reset

wait for link to become ready after reset

#### Synopsis

       int ata_wait_after_reset
       struct ata_link * link
       unsigned long deadline
       int (*check_ready)
         struct ata_link *link

#### Arguments

`link`

  link to be waited on

`deadline`

  deadline jiffies for the operation

`check_ready`

  callback to check link readiness

#### Description

Wait for `link` to become ready after reset.

#### LOCKING

EH context.

#### RETURNS

0 if `linke` is ready before `deadline`; otherwise, -errno.

### LINUX

Kernel Hackers Manual August 2015
sata_link_debounce
9
3.13.0-63-

### sata_link_debounce

debounce SATA phy status

#### Synopsis

       int sata_link_debounce
       struct ata_link * link
       const unsigned long * params
       unsigned long deadline

#### Arguments

`link`

  ATA link to debounce SATA phy status for

`params`

  timing parameters { interval, duratinon, timeout } in msec

`deadline`

  deadline jiffies for the operation

#### Description

Make sure SStatus of `link` reaches stable state, determined by holding the same value where DET is not 1 for `duration` polled every `interval`, before `timeout`. Timeout constraints the beginning of the stable state. Because DET gets stuck at 1 on some controllers after hot unplugging, this functions waits until timeout then returns 0 if DET is stable at 1.

`timeout` is further limited by `deadline`. The sooner of the two is used.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, -errno on failure.

### LINUX

Kernel Hackers Manual August 2015
sata_link_resume
9
3.13.0-63-

### sata_link_resume

resume SATA link

#### Synopsis

       int sata_link_resume
       struct ata_link * link
       const unsigned long * params
       unsigned long deadline

#### Arguments

`link`

  ATA link to resume SATA

`params`

  timing parameters { interval, duratinon, timeout } in msec

`deadline`

  deadline jiffies for the operation

#### Description

Resume SATA phy `link` and debounce it.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, -errno on failure.

### LINUX

Kernel Hackers Manual August 2015
sata_link_scr_lpm
9
3.13.0-63-

### sata_link_scr_lpm

manipulate SControl IPM and SPM fields

#### Synopsis

       int sata_link_scr_lpm
       struct ata_link * link
       enum ata_lpm_policy policy
       bool spm_wakeup

#### Arguments

`link`

  ATA link to manipulate SControl for

`policy`

  LPM policy to configure

`spm_wakeup`

  initiate LPM transition to active state

#### Description

Manipulate the IPM field of the SControl register of `link` according to `policy`. If `policy` is ATA_LPM_MAX_POWER and `spm_wakeup` is `true`, the SPM field is manipulated to wake up the link. This function also clears PHYRDY_CHG before returning.

#### LOCKING

EH context.

#### RETURNS

0 on succes, -errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_std_prereset
9
3.13.0-63-

### ata_std_prereset

prepare for reset

#### Synopsis

       int ata_std_prereset
       struct ata_link * link
       unsigned long deadline

#### Arguments

`link`

  ATA link to be reset

`deadline`

  deadline jiffies for the operation

#### Description

`link` is about to be reset. Initialize it. Failure from prereset makes libata abort whole reset sequence and give up that port, so prereset should be best-effort. It does its best to prepare for reset sequence but if things go wrong, it should just whine, not fail.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, -errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
sata_link_hardreset
9
3.13.0-63-

### sata_link_hardreset

reset link via SATA phy reset

#### Synopsis

       int sata_link_hardreset
       struct ata_link * link
       const unsigned long * timing
       unsigned long deadline
       bool * online
       int (*check_ready)
         struct ata_link *

#### Arguments

`link`

  link to reset

`timing`

  timing parameters { interval, duratinon, timeout } in msec

`deadline`

  deadline jiffies for the operation

`online`

  optional out parameter indicating link onlineness

`check_ready`

  optional callback to check link readiness

#### Description

SATA phy-reset `link` using DET bits of SControl register. After hardreset, link readiness is waited upon using `ata_wait_ready` if `check_ready` is specified. LLDs are allowed to not specify `check_ready` and wait itself after this function returns. Device classification is LLD's responsibility.

*`online` is set to one iff reset succeeded and `link` is online after reset.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, -errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
sata_std_hardreset
9
3.13.0-63-

### sata_std_hardreset

COMRESET w/o waiting or classification

#### Synopsis

       int sata_std_hardreset
       struct ata_link * link
       unsigned int * class
       unsigned long deadline

#### Arguments

`link`

  link to reset

`class`

  resulting class of attached device

`deadline`

  deadline jiffies for the operation

#### Description

Standard SATA COMRESET w/o waiting or classification.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 if link offline, -EAGAIN if link online, -errno on errors.

### LINUX

Kernel Hackers Manual August 2015
ata_std_postreset
9
3.13.0-63-

### ata_std_postreset

standard postreset callback

#### Synopsis

       void ata_std_postreset
       struct ata_link * link
       unsigned int * classes

#### Arguments

`link`

  the target ata_link

`classes`

  classes of attached devices

#### Description

This function is invoked after a successful reset. Note that the device might have been reset more than once using different reset methods before postreset is invoked.

#### LOCKING

Kernel thread context (may sleep)

### LINUX

Kernel Hackers Manual August 2015
ata_dev_set_feature
9
3.13.0-63-

### ata_dev_set_feature

Issue SET FEATURES - SATA FEATURES

#### Synopsis

       unsigned int ata_dev_set_feature
       struct ata_device * dev
       u8 enable
       u8 feature

#### Arguments

`dev`

  Device to which command will be sent

`enable`

  Whether to enable or disable the feature

`feature`

  The sector count represents the feature to set

#### Description

Issue SET FEATURES - SATA FEATURES command to device `dev` on port `ap` with sector count

#### LOCKING

PCI/etc. bus probe sem.

#### RETURNS

0 on success, AC_ERR_* mask otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_std_qc_defer
9
3.13.0-63-

### ata_std_qc_defer

Check whether a qc needs to be deferred

#### Synopsis

       int ata_std_qc_defer
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  ATA command in question

#### Description

Non-NCQ commands cannot run with any other command, NCQ or not. As upper layer only knows the queue depth, we are responsible for maintaining exclusion. This function checks whether a new command `qc` can be issued.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

ATA_DEFER_* if deferring is needed, 0 otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_sg_init
9
3.13.0-63-

### ata_sg_init

Associate command with scatter-gather table.

#### Synopsis

       void ata_sg_init
       struct ata_queued_cmd * qc
       struct scatterlist * sg
       unsigned int n_elem

#### Arguments

`qc`

  Command to be associated

`sg`

  Scatter-gather table.

`n_elem`

  Number of elements in s/g table.

#### Description

Initialize the data-related elements of queued_cmd `qc` to point to a scatter-gather table `sg`, containing `n_elem` elements.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_qc_complete
9
3.13.0-63-

### ata_qc_complete

Complete an active ATA command

#### Synopsis

       void ata_qc_complete
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Command to complete

#### Description

Indicate to the mid and upper layers that an ATA command has completed, with either an ok or not-ok status.

Refrain from calling this function multiple times when successfully completing multiple NCQ commands. `ata_qc_complete_multiple` should be used instead, which will properly update IRQ expect state.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_qc_complete_multiple
9
3.13.0-63-

### ata_qc_complete_multiple

Complete multiple qcs successfully

#### Synopsis

       int ata_qc_complete_multiple
       struct ata_port * ap
       u32 qc_active

#### Arguments

`ap`

  port in question

`qc_active`

  new qc_active mask

#### Description

Complete in-flight commands. This functions is meant to be called from low-level driver's interrupt routine to complete requests normally. ap->qc_active and `qc_active` is compared and commands are completed accordingly.

Always use this function when completing multiple NCQ commands from IRQ handlers instead of calling `ata_qc_complete` multiple times to keep IRQ expect status properly in sync.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Number of completed commands on success, -errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
sata_scr_valid
9
3.13.0-63-

### sata_scr_valid

test whether SCRs are accessible

#### Synopsis

       int sata_scr_valid
       struct ata_link * link

#### Arguments

`link`

  ATA link to test SCR accessibility for

#### Description

Test whether SCRs are accessible for `link`.

#### LOCKING

None.

#### RETURNS

1 if SCRs are accessible, 0 otherwise.

### LINUX

Kernel Hackers Manual August 2015
sata_scr_read
9
3.13.0-63-

### sata_scr_read

read SCR register of the specified port

#### Synopsis

       int sata_scr_read
       struct ata_link * link
       int reg
       u32 * val

#### Arguments

`link`

  ATA link to read SCR for

`reg`

  SCR to read

`val`

  Place to store read value

#### Description

Read SCR register `reg` of `link` into *`val`. This function is guaranteed to succeed if `link` is ap->link, the cable type of the port is SATA and the port implements ->scr_read.

#### LOCKING

None if `link` is ap->link. Kernel thread context otherwise.

#### RETURNS

0 on success, negative errno on failure.

### LINUX

Kernel Hackers Manual August 2015
sata_scr_write
9
3.13.0-63-

### sata_scr_write

write SCR register of the specified port

#### Synopsis

       int sata_scr_write
       struct ata_link * link
       int reg
       u32 val

#### Arguments

`link`

  ATA link to write SCR for

`reg`

  SCR to write

`val`

  value to write

#### Description

Write `val` to SCR register `reg` of `link`. This function is guaranteed to succeed if `link` is ap->link, the cable type of the port is SATA and the port implements ->scr_read.

#### LOCKING

None if `link` is ap->link. Kernel thread context otherwise.

#### RETURNS

0 on success, negative errno on failure.

### LINUX

Kernel Hackers Manual August 2015
sata_scr_write_flush
9
3.13.0-63-

### sata_scr_write_flush

write SCR register of the specified port and flush

#### Synopsis

       int sata_scr_write_flush
       struct ata_link * link
       int reg
       u32 val

#### Arguments

`link`

  ATA link to write SCR for

`reg`

  SCR to write

`val`

  value to write

#### Description

This function is identical to `sata_scr_write` except that this function performs flush after writing to the register.

#### LOCKING

None if `link` is ap->link. Kernel thread context otherwise.

#### RETURNS

0 on success, negative errno on failure.

### LINUX

Kernel Hackers Manual August 2015
ata_link_online
9
3.13.0-63-

### ata_link_online

test whether the given link is online

#### Synopsis

       bool ata_link_online
       struct ata_link * link

#### Arguments

`link`

  ATA link to test

#### Description

Test whether `link` is online. This is identical to `ata_phys_link_online` when there's no slave link. When there's a slave link, this function should only be called on the master link and will return true if any of M/S links is online.

#### LOCKING

None.

#### RETURNS

True if the port online status is available and online.

### LINUX

Kernel Hackers Manual August 2015
ata_link_offline
9
3.13.0-63-

### ata_link_offline

test whether the given link is offline

#### Synopsis

       bool ata_link_offline
       struct ata_link * link

#### Arguments

`link`

  ATA link to test

#### Description

Test whether `link` is offline. This is identical to `ata_phys_link_offline` when there's no slave link. When there's a slave link, this function should only be called on the master link and will return true if both M/S links are offline.

#### LOCKING

None.

#### RETURNS

True if the port offline status is available and offline.

### LINUX

Kernel Hackers Manual August 2015
ata_host_suspend
9
3.13.0-63-

### ata_host_suspend

suspend host

#### Synopsis

       int ata_host_suspend
       struct ata_host * host
       pm_message_t mesg

#### Arguments

`host`

  host to suspend

`mesg`

  PM message

#### Description

Suspend `host`. Actual operation is performed by port suspend.

### LINUX

Kernel Hackers Manual August 2015
ata_host_resume
9
3.13.0-63-

### ata_host_resume

resume host

#### Synopsis

       void ata_host_resume
       struct ata_host * host

#### Arguments

`host`

  host to resume

#### Description

Resume `host`. Actual operation is performed by port resume.

### LINUX

Kernel Hackers Manual August 2015
ata_host_alloc
9
3.13.0-63-

### ata_host_alloc

allocate and init basic ATA host resources

#### Synopsis

       struct ata_host * ata_host_alloc
       struct device * dev
       int max_ports

#### Arguments

`dev`

  generic device this host is associated with

`max_ports`

  maximum number of ATA ports associated with this host

#### Description

Allocate and initialize basic ATA host resources. LLD calls this function to allocate a host, initializes it fully and attaches it using `ata_host_register`.

`max_ports` ports are allocated and host->n_ports is initialized to `max_ports`. The caller is allowed to decrease host->n_ports before calling `ata_host_register`. The unused ports will be automatically freed on registration.

#### RETURNS

Allocate ATA host on success, NULL on failure.

#### LOCKING

Inherited from calling layer (may sleep).

### LINUX

Kernel Hackers Manual August 2015
ata_host_alloc_pinfo
9
3.13.0-63-

### ata_host_alloc_pinfo

alloc host and init with port_info array

#### Synopsis

       struct ata_host * ata_host_alloc_pinfo
       struct device * dev
       const struct ata_port_info *const * ppi
       int n_ports

#### Arguments

`dev`

  generic device this host is associated with

`ppi`

  array of ATA port_info to initialize host with

`n_ports`

  number of ATA ports attached to this host

#### Description

Allocate ATA host and initialize with info from `ppi`. If NULL terminated, `ppi` may contain fewer entries than `n_ports`. The last entry will be used for the remaining ports.

#### RETURNS

Allocate ATA host on success, NULL on failure.

#### LOCKING

Inherited from calling layer (may sleep).

### LINUX

Kernel Hackers Manual August 2015
ata_slave_link_init
9
3.13.0-63-

### ata_slave_link_init

initialize slave link

#### Synopsis

       int ata_slave_link_init
       struct ata_port * ap

#### Arguments

`ap`

  port to initialize slave link for

#### Description

Create and initialize slave link for `ap`. This enables slave link handling on the port.

In libata, a port contains links and a link contains devices. There is single host link but if a PMP is attached to it, there can be multiple fan-out links. On SATA, there's usually a single device connected to a link but PATA and SATA controllers emulating TF based interface can have two - master and slave.

However, there are a few controllers which don't fit into this abstraction too well - SATA controllers which emulate TF interface with both master and slave devices but also have separate SCR register sets for each device. These controllers need separate links for physical link handling (e.g. onlineness, link speed) but should be treated like a traditional M/S controller for everything else (e.g. command issue, softreset).

slave_link is libata's way of handling this class of controllers without impacting core layer too much. For anything other than physical link handling, the default host link is used for both master and slave. For physical link handling, separate `ap`->slave_link is used. All dirty details are implemented inside libata core layer. From LLD's POV, the only difference is that prereset, hardreset and postreset are called once more for the slave link, so the reset sequence looks like the following.

prereset(M) -> prereset(S) -> hardreset(M) -> hardreset(S) -> softreset(M) -> postreset(M) -> postreset(S)

Note that softreset is called only for the master. Softreset resets both M/S by definition, so SRST on master should handle both (the standard method will work just fine).

#### LOCKING

Should be called before host is registered.

#### RETURNS

0 on success, -errno on failure.

### LINUX

Kernel Hackers Manual August 2015
ata_host_start
9
3.13.0-63-

### ata_host_start

start and freeze ports of an ATA host

#### Synopsis

       int ata_host_start
       struct ata_host * host

#### Arguments

`host`

  ATA host to start ports for

#### Description

Start and then freeze ports of `host`. Started status is recorded in host->flags, so this function can be called multiple times. Ports are guaranteed to get started only once. If host->ops isn't initialized yet, its set to the first non-dummy port ops.

#### LOCKING

Inherited from calling layer (may sleep).

#### RETURNS

0 if all ports are started successfully, -errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_host_init
9
3.13.0-63-

### ata_host_init

Initialize a host struct for sas (ipr, libsas)

#### Synopsis

       void ata_host_init
       struct ata_host * host
       struct device * dev
       struct ata_port_operations * ops

#### Arguments

`host`

  host to initialize

`dev`

  device host is attached to

`ops`

  port_ops

### LINUX

Kernel Hackers Manual August 2015
ata_host_register
9
3.13.0-63-

### ata_host_register

register initialized ATA host

#### Synopsis

       int ata_host_register
       struct ata_host * host
       struct scsi_host_template * sht

#### Arguments

`host`

  ATA host to register

`sht`

  template for SCSI host

#### Description

Register initialized ATA host. `host` is allocated using `ata_host_alloc` and fully initialized by LLD. This function starts ports, registers `host` with ATA and SCSI layers and probe registered devices.

#### LOCKING

Inherited from calling layer (may sleep).

#### RETURNS

0 on success, -errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_host_activate
9
3.13.0-63-

### ata_host_activate

start host, request IRQ and register it

#### Synopsis

       int ata_host_activate
       struct ata_host * host
       int irq
       irq_handler_t irq_handler
       unsigned long irq_flags
       struct scsi_host_template * sht

#### Arguments

`host`

  target ATA host

`irq`

  IRQ to request

`irq_handler`

  irq_handler used when requesting IRQ

`irq_flags`

  irq_flags used when requesting IRQ

`sht`

  scsi_host_template to use when registering the host

#### Description

After allocating an ATA host and initializing it, most libata LLDs perform three steps to activate the host - start host, request IRQ and register it. This helper takes necessasry arguments and performs the three steps in one go.

An invalid IRQ skips the IRQ registration and expects the host to have set polling mode on the port. In this case, `irq_handler` should be NULL.

#### LOCKING

Inherited from calling layer (may sleep).

#### RETURNS

0 on success, -errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_host_detach
9
3.13.0-63-

### ata_host_detach

Detach all ports of an ATA host

#### Synopsis

       void ata_host_detach
       struct ata_host * host

#### Arguments

`host`

  Host to detach

#### Description

Detach all ports of `host`.

#### LOCKING

Kernel thread context (may sleep).

### LINUX

Kernel Hackers Manual August 2015
ata_pci_remove_one
9
3.13.0-63-

### ata_pci_remove_one

PCI layer callback for device removal

#### Synopsis

       void ata_pci_remove_one
       struct pci_dev * pdev

#### Arguments

`pdev`

  PCI device that was removed

#### Description

PCI layer indicates to libata via this hook that hot-unplug or module unload event has occurred. Detach all ports. Resource release is handled via devres.

#### LOCKING

Inherited from PCI layer (may sleep).

### LINUX

Kernel Hackers Manual August 2015
ata_platform_remove_one
9
3.13.0-63-

### ata_platform_remove_one

Platform layer callback for device removal

#### Synopsis

       int ata_platform_remove_one
       struct platform_device * pdev

#### Arguments

`pdev`

  Platform device that was removed

#### Description

Platform layer indicates to libata via this hook that hot-unplug or module unload event has occurred. Detach all ports. Resource release is handled via devres.

#### LOCKING

Inherited from platform layer (may sleep).

### LINUX

Kernel Hackers Manual August 2015
ata_msleep
9
3.13.0-63-

### ata_msleep

ATA EH owner aware msleep

#### Synopsis

       void ata_msleep
       struct ata_port * ap
       unsigned int msecs

#### Arguments

`ap`

  ATA port to attribute the sleep to

`msecs`

  duration to sleep in milliseconds

#### Description

Sleeps `msecs`. If the current task is owner of `ap`'s EH, the ownership is released before going to sleep and reacquired after the sleep is complete. IOW, other ports sharing the `ap`->host will be allowed to own the EH while this task is sleeping.

#### LOCKING

Might sleep.

### LINUX

Kernel Hackers Manual August 2015
ata_wait_register
9
3.13.0-63-

### ata_wait_register

wait until register value changes

#### Synopsis

       u32 ata_wait_register
       struct ata_port * ap
       void __iomem * reg
       u32 mask
       u32 val
       unsigned long interval
       unsigned long timeout

#### Arguments

`ap`

  ATA port to wait register for, can be NULL

`reg`

  IO-mapped register

`mask`

  Mask to apply to read register value

`val`

  Wait condition

`interval`

  polling interval in milliseconds

`timeout`

  timeout in milliseconds

#### Description

Waiting for some bits of register to change is a common operation for ATA controllers. This function reads 32bit LE IO-mapped register `reg` and tests for the following condition.

(*`reg` & mask) != val

If the condition is met, it returns; otherwise, the process is repeated after `interval_msec` until timeout.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

The final register value.

### LINUX

Kernel Hackers Manual August 2015
sata_lpm_ignore_phy_events
9
3.13.0-63-

### sata_lpm_ignore_phy_events

test if PHY event should be ignored

#### Synopsis

       bool sata_lpm_ignore_phy_events
       struct ata_link * link

#### Arguments

`link`

  Link receiving the event

#### Description

Test whether the received PHY event has to be ignored or not.

#### RETURNS

True if the event has to be ignored.

## libata Core Internals

### LINUX

Kernel Hackers Manual August 2015
ata_dev_phys_link
9
3.13.0-63-

### ata_dev_phys_link

find physical link for a device

#### Synopsis

       struct ata_link * ata_dev_phys_link
       struct ata_device * dev

#### Arguments

`dev`

  ATA device to look up physical link for

#### Description

Look up physical link which `dev` is attached to. Note that this is different from `dev`->link only when `dev` is on slave link. For all other cases, it's the same as `dev`->link.

#### LOCKING

Don't care.

#### RETURNS

Pointer to the found physical link.

### LINUX

Kernel Hackers Manual August 2015
ata_force_cbl
9
3.13.0-63-

### ata_force_cbl

force cable type according to libata.force

#### Synopsis

       void ata_force_cbl
       struct ata_port * ap

#### Arguments

`ap`

  ATA port of interest

#### Description

Force cable type according to libata.force and whine about it. The last entry which has matching port number is used, so it can be specified as part of device force parameters. For example, both a:40c,1.00:udma4 and 1.00:40c,udma4 have the same effect.

#### LOCKING

EH context.

### LINUX

Kernel Hackers Manual August 2015
ata_force_link_limits
9
3.13.0-63-

### ata_force_link_limits

force link limits according to libata.force

#### Synopsis

       void ata_force_link_limits
       struct ata_link * link

#### Arguments

`link`

  ATA link of interest

#### Description

Force link flags and SATA spd limit according to libata.force and whine about it. When only the port part is specified (e.g. 1:), the limit applies to all links connected to both the host link and all fan-out ports connected via PMP. If the device part is specified as 0 (e.g. 1.00:), it specifies the first fan-out link not the host link. Device number 15 always points to the host link whether PMP is attached or not. If the controller has slave link, device number 16 points to it.

#### LOCKING

EH context.

### LINUX

Kernel Hackers Manual August 2015
ata_force_xfermask
9
3.13.0-63-

### ata_force_xfermask

force xfermask according to libata.force

#### Synopsis

       void ata_force_xfermask
       struct ata_device * dev

#### Arguments

`dev`

  ATA device of interest

#### Description

Force xfer_mask according to libata.force and whine about it. For consistency with link selection, device number 15 selects the first device connected to the host link.

#### LOCKING

EH context.

### LINUX

Kernel Hackers Manual August 2015
ata_force_horkage
9
3.13.0-63-

### ata_force_horkage

force horkage according to libata.force

#### Synopsis

       void ata_force_horkage
       struct ata_device * dev

#### Arguments

`dev`

  ATA device of interest

#### Description

Force horkage according to libata.force and whine about it. For consistency with link selection, device number 15 selects the first device connected to the host link.

#### LOCKING

EH context.

### LINUX

Kernel Hackers Manual August 2015
ata_rwcmd_protocol
9
3.13.0-63-

### ata_rwcmd_protocol

set taskfile r/w commands and protocol

#### Synopsis

       int ata_rwcmd_protocol
       struct ata_taskfile * tf
       struct ata_device * dev

#### Arguments

`tf`

  command to examine and configure

`dev`

  device tf belongs to

#### Description

Examine the device configuration and tf->flags to calculate the proper read/write commands and protocol to use.

#### LOCKING

caller.

### LINUX

Kernel Hackers Manual August 2015
ata_tf_read_block
9
3.13.0-63-

### ata_tf_read_block

Read block address from ATA taskfile

#### Synopsis

       u64 ata_tf_read_block
       struct ata_taskfile * tf
       struct ata_device * dev

#### Arguments

`tf`

  ATA taskfile of interest

`dev`

  ATA device `tf` belongs to

#### LOCKING

None.

Read block address from `tf`. This function can handle all three address formats - LBA, LBA48 and CHS. tf->protocol and flags select the address format to use.

#### RETURNS

Block address read from `tf`.

### LINUX

Kernel Hackers Manual August 2015
ata_build_rw_tf
9
3.13.0-63-

### ata_build_rw_tf

Build ATA taskfile for given read/write request

#### Synopsis

       int ata_build_rw_tf
       struct ata_taskfile * tf
       struct ata_device * dev
       u64 block
       u32 n_block
       unsigned int tf_flags
       unsigned int tag

#### Arguments

`tf`

  Target ATA taskfile

`dev`

  ATA device `tf` belongs to

`block`

  Block address

`n_block`

  Number of blocks

`tf_flags`

  RW/FUA etc...

`tag`

  tag

#### LOCKING

None.

Build ATA taskfile `tf` for read/write request described by `block`, `n_block`, `tf_flags` and `tag` on `dev`.

#### RETURNS

0 on success, -ERANGE if the request is too large for `dev`, -EINVAL if the request is invalid.

### LINUX

Kernel Hackers Manual August 2015
ata_read_native_max_address
9
3.13.0-63-

### ata_read_native_max_address

Read native max address

#### Synopsis

       int ata_read_native_max_address
       struct ata_device * dev
       u64 * max_sectors

#### Arguments

`dev`

  target device

`max_sectors`

  out parameter for the result native max address

#### Description

Perform an LBA48 or LBA28 native size query upon the device in question.

#### RETURNS

0 on success, -EACCES if command is aborted by the drive. -EIO on other errors.

### LINUX

Kernel Hackers Manual August 2015
ata_set_max_sectors
9
3.13.0-63-

### ata_set_max_sectors

Set max sectors

#### Synopsis

       int ata_set_max_sectors
       struct ata_device * dev
       u64 new_sectors

#### Arguments

`dev`

  target device

`new_sectors`

  new max sectors value to set for the device

#### Description

Set max sectors of `dev` to `new_sectors`.

#### RETURNS

0 on success, -EACCES if command is aborted or denied (due to previous non-volatile SET_MAX) by the drive. -EIO on other errors.

### LINUX

Kernel Hackers Manual August 2015
ata_hpa_resize
9
3.13.0-63-

### ata_hpa_resize

Resize a device with an HPA set

#### Synopsis

       int ata_hpa_resize
       struct ata_device * dev

#### Arguments

`dev`

  Device to resize

#### Description

Read the size of an LBA28 or LBA48 disk with HPA features and resize it if required to the full size of the media. The caller must check the drive has the HPA feature set enabled.

#### RETURNS

0 on success, -errno on failure.

### LINUX

Kernel Hackers Manual August 2015
ata_dump_id
9
3.13.0-63-

### ata_dump_id

IDENTIFY DEVICE info debugging output

#### Synopsis

       void ata_dump_id
       const u16 * id

#### Arguments

`id`

  IDENTIFY DEVICE page to dump

#### Description

Dump selected 16-bit words from the given IDENTIFY DEVICE page.

#### LOCKING

caller.

### LINUX

Kernel Hackers Manual August 2015
ata_exec_internal_sg
9
3.13.0-63-

### ata_exec_internal_sg

execute libata internal command

#### Synopsis

       unsigned ata_exec_internal_sg
       struct ata_device * dev
       struct ata_taskfile * tf
       const u8 * cdb
       int dma_dir
       struct scatterlist * sgl
       unsigned int n_elem
       unsigned long timeout

#### Arguments

`dev`

  Device to which the command is sent

`tf`

  Taskfile registers for the command and the result

`cdb`

  CDB for packet command

`dma_dir`

  Data tranfer direction of the command

`sgl`

  sg list for the data buffer of the command

`n_elem`

  Number of sg entries

`timeout`

  Timeout in msecs (0 for default)

#### Description

Executes libata internal command with timeout. `tf` contains command on entry and result on return. Timeout and error conditions are reported via return value. No recovery action is taken after a command times out. It's caller's duty to clean up after timeout.

#### LOCKING

None. Should be called with kernel context, might sleep.

#### RETURNS

Zero on success, AC_ERR_* mask on failure

### LINUX

Kernel Hackers Manual August 2015
ata_exec_internal
9
3.13.0-63-

### ata_exec_internal

execute libata internal command

#### Synopsis

       unsigned ata_exec_internal
       struct ata_device * dev
       struct ata_taskfile * tf
       const u8 * cdb
       int dma_dir
       void * buf
       unsigned int buflen
       unsigned long timeout

#### Arguments

`dev`

  Device to which the command is sent

`tf`

  Taskfile registers for the command and the result

`cdb`

  CDB for packet command

`dma_dir`

  Data tranfer direction of the command

`buf`

  Data buffer of the command

`buflen`

  Length of data buffer

`timeout`

  Timeout in msecs (0 for default)

#### Description

Wrapper around `ata_exec_internal_sg` which takes simple buffer instead of sg list.

#### LOCKING

None. Should be called with kernel context, might sleep.

#### RETURNS

Zero on success, AC_ERR_* mask on failure

### LINUX

Kernel Hackers Manual August 2015
ata_do_simple_cmd
9
3.13.0-63-

### ata_do_simple_cmd

execute simple internal command

#### Synopsis

       unsigned int ata_do_simple_cmd
       struct ata_device * dev
       u8 cmd

#### Arguments

`dev`

  Device to which the command is sent

`cmd`

  Opcode to execute

#### Description

Execute a 'simple' command, that only consists of the opcode 'cmd' itself, without filling any other registers

#### LOCKING

Kernel thread context (may sleep).

#### RETURNS

Zero on success, AC_ERR_* mask on failure

### LINUX

Kernel Hackers Manual August 2015
ata_pio_mask_no_iordy
9
3.13.0-63-

### ata_pio_mask_no_iordy

Return the non IORDY mask

#### Synopsis

       u32 ata_pio_mask_no_iordy
       const struct ata_device * adev

#### Arguments

`adev`

  ATA device

#### Description

Compute the highest mode possible if we are not using iordy. Return -1 if no iordy mode is available.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_read_id
9
3.13.0-63-

### ata_dev_read_id

Read ID data from the specified device

#### Synopsis

       int ata_dev_read_id
       struct ata_device * dev
       unsigned int * p_class
       unsigned int flags
       u16 * id

#### Arguments

`dev`

  target device

`p_class`

  pointer to class of the target device (may be changed)

`flags`

  ATA_READID_* flags

`id`

  buffer to read IDENTIFY data into

#### Description

Read ID data from the specified device. ATA_CMD_ID_ATA is performed on ATA devices and ATA_CMD_ID_ATAPI on ATAPI devices. This function also issues ATA_CMD_INIT_DEV_PARAMS for pre-ATA4 drives.

#### FIXME

ATA_CMD_ID_ATA is optional for early drives and right now we abort if we hit that case.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, -errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_configure
9
3.13.0-63-

### ata_dev_configure

Configure the specified ATA/ATAPI device

#### Synopsis

       int ata_dev_configure
       struct ata_device * dev

#### Arguments

`dev`

  Target device to configure

#### Description

Configure `dev` according to `dev`->id. Generic and low-level driver specific fixups are also applied.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, -errno otherwise

### LINUX

Kernel Hackers Manual August 2015
ata_bus_probe
9
3.13.0-63-

### ata_bus_probe

Reset and probe ATA bus

#### Synopsis

       int ata_bus_probe
       struct ata_port * ap

#### Arguments

`ap`

  Bus to probe

#### Description

Master ATA bus probing function. Initiates a hardware-dependent bus reset, then attempts to identify any devices found on the bus.

#### LOCKING

PCI/etc. bus probe sem.

#### RETURNS

Zero on success, negative errno otherwise.

### LINUX

Kernel Hackers Manual August 2015
sata_print_link_status
9
3.13.0-63-

### sata_print_link_status

Print SATA link status

#### Synopsis

       void sata_print_link_status
       struct ata_link * link

#### Arguments

`link`

  SATA link to printk link status about

#### Description

This function prints link speed and status of a SATA link.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
sata_down_spd_limit
9
3.13.0-63-

### sata_down_spd_limit

adjust SATA spd limit downward

#### Synopsis

       int sata_down_spd_limit
       struct ata_link * link
       u32 spd_limit

#### Arguments

`link`

  Link to adjust SATA spd limit for

`spd_limit`

  Additional limit

#### Description

Adjust SATA spd limit of `link` downward. Note that this function only adjusts the limit. The change must be applied using `sata_set_spd`.

If `spd_limit` is non-zero, the speed is limited to equal to or lower than `spd_limit` if such speed is supported. If `spd_limit` is slower than any supported speed, only the lowest supported speed is allowed.

#### LOCKING

Inherited from caller.

#### RETURNS

0 on success, negative errno on failure

### LINUX

Kernel Hackers Manual August 2015
sata_set_spd_needed
9
3.13.0-63-

### sata_set_spd_needed

is SATA spd configuration needed

#### Synopsis

       int sata_set_spd_needed
       struct ata_link * link

#### Arguments

`link`

  Link in question

#### Description

Test whether the spd limit in SControl matches `link`->sata_spd_limit. This function is used to determine whether hardreset is necessary to apply SATA spd configuration.

#### LOCKING

Inherited from caller.

#### RETURNS

1 if SATA spd configuration is needed, 0 otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_down_xfermask_limit
9
3.13.0-63-

### ata_down_xfermask_limit

adjust dev xfer masks downward

#### Synopsis

       int ata_down_xfermask_limit
       struct ata_device * dev
       unsigned int sel

#### Arguments

`dev`

  Device to adjust xfer masks

`sel`

  ATA_DNXFER_* selector

#### Description

Adjust xfer masks of `dev` downward. Note that this function does not apply the change. Invoking `ata_set_mode` afterwards will apply the limit.

#### LOCKING

Inherited from caller.

#### RETURNS

0 on success, negative errno on failure

### LINUX

Kernel Hackers Manual August 2015
ata_wait_ready
9
3.13.0-63-

### ata_wait_ready

wait for link to become ready

#### Synopsis

       int ata_wait_ready
       struct ata_link * link
       unsigned long deadline
       int (*check_ready)
         struct ata_link *link

#### Arguments

`link`

  link to be waited on

`deadline`

  deadline jiffies for the operation

`check_ready`

  callback to check link readiness

#### Description

Wait for `link` to become ready. `check_ready` should return positive number if `link` is ready, 0 if it isn't, -ENODEV if link doesn't seem to be occupied, other errno for other error conditions.

Transient -ENODEV conditions are allowed for ATA_TMOUT_FF_WAIT.

#### LOCKING

EH context.

#### RETURNS

0 if `linke` is ready before `deadline`; otherwise, -errno.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_same_device
9
3.13.0-63-

### ata_dev_same_device

Determine whether new ID matches configured device

#### Synopsis

       int ata_dev_same_device
       struct ata_device * dev
       unsigned int new_class
       const u16 * new_id

#### Arguments

`dev`

  device to compare against

`new_class`

  class of the new device

`new_id`

  IDENTIFY page of the new device

#### Description

Compare `new_class` and `new_id` against `dev` and determine whether `dev` is the device indicated by `new_class` and `new_id`.

#### LOCKING

None.

#### RETURNS

1 if `dev` matches `new_class` and `new_id`, 0 otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_reread_id
9
3.13.0-63-

### ata_dev_reread_id

Re-read IDENTIFY data

#### Synopsis

       int ata_dev_reread_id
       struct ata_device * dev
       unsigned int readid_flags

#### Arguments

`dev`

  target ATA device

`readid_flags`

  read ID flags

#### Description

Re-read IDENTIFY page and make sure `dev` is still attached to the port.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, negative errno otherwise

### LINUX

Kernel Hackers Manual August 2015
ata_dev_revalidate
9
3.13.0-63-

### ata_dev_revalidate

Revalidate ATA device

#### Synopsis

       int ata_dev_revalidate
       struct ata_device * dev
       unsigned int new_class
       unsigned int readid_flags

#### Arguments

`dev`

  device to revalidate

`new_class`

  new class code

`readid_flags`

  read ID flags

#### Description

Re-read IDENTIFY page, make sure `dev` is still attached to the port and reconfigure it according to the new IDENTIFY page.

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, negative errno otherwise

### LINUX

Kernel Hackers Manual August 2015
glob_match
9
3.13.0-63-

### glob_match

match a text string against a glob-style pattern

#### Synopsis

       int glob_match
       const char * text
       const char * pattern

#### Arguments

`text`

  the string to be examined

`pattern`

  the glob-style pattern to be matched against

#### Description

Either/both of text and pattern can be empty strings.

Match text against a glob-style pattern, with wildcards and simple sets:

? matches any single character. * matches any run of characters. [xyz] matches a single character from the set: x, y, or z. [a-d] matches a single character from the range: a, b, c, or d. [a-d0-9] matches a single character from either range.

The special characters ?, [, -, or *, can be matched using a set, eg. [*] Behaviour with malformed patterns is undefined, though generally reasonable.

#### Sample patterns

"SD1?, SD1[0-5], *R0, SD*1?[012]*xx"

This function uses one level of recursion per '*' in pattern. Since it calls _nothing_ else, and has _no_ explicit local variables, this will not cause stack problems for any reasonable use here.

#### RETURNS

0 on match, 1 otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_is_40wire
9
3.13.0-63-

### ata_is_40wire

check drive side detection

#### Synopsis

       int ata_is_40wire
       struct ata_device * dev

#### Arguments

`dev`

  device

#### Description

Perform drive side detection decoding, allowing for device vendors who can't follow the documentation.

### LINUX

Kernel Hackers Manual August 2015
cable_is_40wire
9
3.13.0-63-

### cable_is_40wire

40/80/SATA decider

#### Synopsis

       int cable_is_40wire
       struct ata_port * ap

#### Arguments

`ap`

  port to consider

#### Description

This function encapsulates the policy for speed management in one place. At the moment we don't cache the result but there is a good case for setting ap->cbl to the result when we are called with unknown cables (and figuring out if it impacts hotplug at all).

Return 1 if the cable appears to be 40 wire.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_xfermask
9
3.13.0-63-

### ata_dev_xfermask

Compute supported xfermask of the given device

#### Synopsis

       void ata_dev_xfermask
       struct ata_device * dev

#### Arguments

`dev`

  Device to compute xfermask for

#### Description

Compute supported xfermask of `dev` and store it in dev->*_mask. This function is responsible for applying all known limits including host controller limits, device blacklist, etc...

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_set_xfermode
9
3.13.0-63-

### ata_dev_set_xfermode

Issue SET FEATURES - XFER MODE command

#### Synopsis

       unsigned int ata_dev_set_xfermode
       struct ata_device * dev

#### Arguments

`dev`

  Device to which command will be sent

#### Description

Issue SET FEATURES - XFER MODE command to device `dev` on port `ap`.

#### LOCKING

PCI/etc. bus probe sem.

#### RETURNS

0 on success, AC_ERR_* mask otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_init_params
9
3.13.0-63-

### ata_dev_init_params

Issue INIT DEV PARAMS command

#### Synopsis

       unsigned int ata_dev_init_params
       struct ata_device * dev
       u16 heads
       u16 sectors

#### Arguments

`dev`

  Device to which command will be sent

`heads`

  Number of heads (taskfile parameter)

`sectors`

  Number of sectors (taskfile parameter)

#### LOCKING

Kernel thread context (may sleep)

#### RETURNS

0 on success, AC_ERR_* mask otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_sg_clean
9
3.13.0-63-

### ata_sg_clean

Unmap DMA memory associated with command

#### Synopsis

       void ata_sg_clean
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Command containing DMA memory to be released

#### Description

Unmap all mapped DMA memory associated with this command.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
atapi_check_dma
9
3.13.0-63-

### atapi_check_dma

Check whether ATAPI DMA can be supported

#### Synopsis

       int atapi_check_dma
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Metadata associated with taskfile to check

#### Description

Allow low-level driver to filter ATA PACKET commands, returning a status indicating whether or not it is OK to use DMA for the supplied PACKET command.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

0 when ATAPI DMA can be used nonzero otherwise

### LINUX

Kernel Hackers Manual August 2015
ata_sg_setup
9
3.13.0-63-

### ata_sg_setup

DMA-map the scatter-gather table associated with a command.

#### Synopsis

       int ata_sg_setup
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Command with scatter-gather table to be mapped.

#### Description

DMA-map the scatter-gather table associated with queued_cmd `qc`.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Zero on success, negative on error.

### LINUX

Kernel Hackers Manual August 2015
swap_buf_le16
9
3.13.0-63-

### swap_buf_le16

swap halves of 16-bit words in place

#### Synopsis

       void swap_buf_le16
       u16 * buf
       unsigned int buf_words

#### Arguments

`buf`

  Buffer to swap

`buf_words`

  Number of 16-bit words in buffer.

#### Description

Swap halves of 16-bit words if needed to convert from little-endian byte order to native cpu byte order, or vice-versa.

#### LOCKING

Inherited from caller.

### LINUX

Kernel Hackers Manual August 2015
ata_qc_new
9
3.13.0-63-

### ata_qc_new

Request an available ATA command, for queueing

#### Synopsis

       struct ata_queued_cmd * ata_qc_new
       struct ata_port * ap

#### Arguments

`ap`

  target port

#### Description

Some ATA host controllers may implement a queue depth which is less than ATA_MAX_QUEUE. So we shouldn't allocate a tag which is beyond the hardware limitation.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_qc_new_init
9
3.13.0-63-

### ata_qc_new_init

Request an available ATA command, and initialize it

#### Synopsis

       struct ata_queued_cmd * ata_qc_new_init
       struct ata_device * dev

#### Arguments

`dev`

  Device from whom we request an available command structure

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_qc_free
9
3.13.0-63-

### ata_qc_free

free unused ata_queued_cmd

#### Synopsis

       void ata_qc_free
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Command to complete

#### Description

Designed to free unused ata_queued_cmd object in case something prevents using it.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_qc_issue
9
3.13.0-63-

### ata_qc_issue

issue taskfile to device

#### Synopsis

       void ata_qc_issue
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  command to issue to device

#### Description

Prepare an ATA command to submission to device. This includes mapping the data into a DMA-able area, filling in the S/G table, and finally writing the taskfile to hardware, starting the command.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_phys_link_online
9
3.13.0-63-

### ata_phys_link_online

test whether the given link is online

#### Synopsis

       bool ata_phys_link_online
       struct ata_link * link

#### Arguments

`link`

  ATA link to test

#### Description

Test whether `link` is online. Note that this function returns 0 if online status of `link` cannot be obtained, so ata_link_online(link) != !ata_link_offline(link).

#### LOCKING

None.

#### RETURNS

True if the port online status is available and online.

### LINUX

Kernel Hackers Manual August 2015
ata_phys_link_offline
9
3.13.0-63-

### ata_phys_link_offline

test whether the given link is offline

#### Synopsis

       bool ata_phys_link_offline
       struct ata_link * link

#### Arguments

`link`

  ATA link to test

#### Description

Test whether `link` is offline. Note that this function returns 0 if offline status of `link` cannot be obtained, so ata_link_online(link) != !ata_link_offline(link).

#### LOCKING

None.

#### RETURNS

True if the port offline status is available and offline.

### LINUX

Kernel Hackers Manual August 2015
ata_dev_init
9
3.13.0-63-

### ata_dev_init

Initialize an ata_device structure

#### Synopsis

       void ata_dev_init
       struct ata_device * dev

#### Arguments

`dev`

  Device structure to initialize

#### Description

Initialize `dev` in preparation for probing.

#### LOCKING

Inherited from caller.

### LINUX

Kernel Hackers Manual August 2015
ata_link_init
9
3.13.0-63-

### ata_link_init

Initialize an ata_link structure

#### Synopsis

       void ata_link_init
       struct ata_port * ap
       struct ata_link * link
       int pmp

#### Arguments

`ap`

  ATA port link is attached to

`link`

  Link structure to initialize

`pmp`

  Port multiplier port number

#### Description

Initialize `link`.

#### LOCKING

Kernel thread context (may sleep)

### LINUX

Kernel Hackers Manual August 2015
sata_link_init_spd
9
3.13.0-63-

### sata_link_init_spd

Initialize link->sata_spd_limit

#### Synopsis

       int sata_link_init_spd
       struct ata_link * link

#### Arguments

`link`

  Link to configure sata_spd_limit for

#### Description

Initialize `link`->[hw_]sata_spd_limit to the currently configured value.

#### LOCKING

Kernel thread context (may sleep).

#### RETURNS

0 on success, -errno on failure.

### LINUX

Kernel Hackers Manual August 2015
ata_port_alloc
9
3.13.0-63-

### ata_port_alloc

allocate and initialize basic ATA port resources

#### Synopsis

       struct ata_port * ata_port_alloc
       struct ata_host * host

#### Arguments

`host`

  ATA host this allocated port belongs to

#### Description

Allocate and initialize basic ATA port resources.

#### RETURNS

Allocate ATA port on success, NULL on failure.

#### LOCKING

Inherited from calling layer (may sleep).

### LINUX

Kernel Hackers Manual August 2015
ata_finalize_port_ops
9
3.13.0-63-

### ata_finalize_port_ops

finalize ata_port_operations

#### Synopsis

       void ata_finalize_port_ops
       struct ata_port_operations * ops

#### Arguments

`ops`

  ata_port_operations to finalize

#### Description

An ata_port_operations can inherit from another ops and that ops can again inherit from another. This can go on as many times as necessary as long as there is no loop in the inheritance chain.

Ops tables are finalized when the host is started. NULL or unspecified entries are inherited from the closet ancestor which has the method and the entry is populated with it. After finalization, the ops table directly points to all the methods and ->inherits is no longer necessary and cleared.

Using ATA_OP_NULL, inheriting ops can force a method to NULL.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_port_detach
9
3.13.0-63-

### ata_port_detach

Detach ATA port in prepration of device removal

#### Synopsis

       void ata_port_detach
       struct ata_port * ap

#### Arguments

`ap`

  ATA port to be detached

#### Description

Detach all ATA devices and the associated SCSI devices of `ap`; then, remove the associated SCSI host. `ap` is guaranteed to be quiescent on return from this function.

#### LOCKING

Kernel thread context (may sleep).

## libata SCSI translation/emulation

### LINUX

Kernel Hackers Manual August 2015
ata_std_bios_param
9
3.13.0-63-

### ata_std_bios_param

generic bios head/sector/cylinder calculator used by sd.

#### Synopsis

       int ata_std_bios_param
       struct scsi_device * sdev
       struct block_device * bdev
       sector_t capacity
       int geom[]

#### Arguments

`sdev`

  SCSI device for which BIOS geometry is to be determined

`bdev`

  block device associated with `sdev`

`capacity`

  capacity of SCSI device

`geom[]`

  location to which geometry will be output

#### Description

Generic bios head/sector/cylinder calculator used by sd. Most BIOSes nowadays expect a XXX/255/16 (CHS) mapping. Some situations may arise where the disk is not bootable if this is not used.

#### LOCKING

Defined by the SCSI layer. We don't really care.

#### RETURNS

Zero.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_unlock_native_capacity
9
3.13.0-63-

### ata_scsi_unlock_native_capacity

unlock native capacity

#### Synopsis

       void ata_scsi_unlock_native_capacity
       struct scsi_device * sdev

#### Arguments

`sdev`

  SCSI device to adjust device capacity for

#### Description

This function is called if a partition on `sdev` extends beyond the end of the device. It requests EH to unlock HPA.

#### LOCKING

Defined by the SCSI layer. Might sleep.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_slave_config
9
3.13.0-63-

### ata_scsi_slave_config

Set SCSI device attributes

#### Synopsis

       int ata_scsi_slave_config
       struct scsi_device * sdev

#### Arguments

`sdev`

  SCSI device to examine

#### Description

This is called before we actually start reading and writing to the device, to configure certain SCSI mid-layer behaviors.

#### LOCKING

Defined by SCSI layer. We don't really care.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_slave_destroy
9
3.13.0-63-

### ata_scsi_slave_destroy

SCSI device is about to be destroyed

#### Synopsis

       void ata_scsi_slave_destroy
       struct scsi_device * sdev

#### Arguments

`sdev`

  SCSI device to be destroyed

#### Description

`sdev` is about to be destroyed for hot/warm unplugging. If this unplugging was initiated by libata as indicated by NULL dev->sdev, this function doesn't have to do anything. Otherwise, SCSI layer initiated warm-unplug is in progress. Clear dev->sdev, schedule the device for ATA detach and invoke EH.

#### LOCKING

Defined by SCSI layer. We don't really care.

### LINUX

Kernel Hackers Manual August 2015
__ata_change_queue_depth
9
3.13.0-63-

### __ata_change_queue_depth

helper for ata_scsi_change_queue_depth

#### Synopsis

       int __ata_change_queue_depth
       struct ata_port * ap
       struct scsi_device * sdev
       int queue_depth
       int reason

#### Arguments

`ap`

  ATA port to which the device change the queue depth

`sdev`

  SCSI device to configure queue depth for

`queue_depth`

  new queue depth

`reason`

  calling context

#### Description

libsas and libata have different approaches for associating a sdev to its ata_port.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_change_queue_depth
9
3.13.0-63-

### ata_scsi_change_queue_depth

SCSI callback for queue depth config

#### Synopsis

       int ata_scsi_change_queue_depth
       struct scsi_device * sdev
       int queue_depth
       int reason

#### Arguments

`sdev`

  SCSI device to configure queue depth for

`queue_depth`

  new queue depth

`reason`

  calling context

#### Description

This is libata standard hostt->change_queue_depth callback. SCSI will call into this callback when user tries to set queue depth via sysfs.

#### LOCKING

SCSI layer (we don't care)

#### RETURNS

Newly configured queue depth.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_queuecmd
9
3.13.0-63-

### ata_scsi_queuecmd

Issue SCSI cdb to libata-managed device

#### Synopsis

       int ata_scsi_queuecmd
       struct Scsi_Host * shost
       struct scsi_cmnd * cmd

#### Arguments

`shost`

  SCSI host of command to be sent

`cmd`

  SCSI command to be sent

#### Description

In some cases, this function translates SCSI commands into ATA taskfiles, and queues the taskfiles to be sent to hardware. In other cases, this function simulates a SCSI device by evaluating and responding to certain SCSI commands. This creates the overall effect of ATA and ATAPI devices appearing as SCSI devices.

#### LOCKING

ATA host lock

#### RETURNS

Return value from `__ata_scsi_queuecmd` if `cmd` can be queued, 0 otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_simulate
9
3.13.0-63-

### ata_scsi_simulate

simulate SCSI command on ATA device

#### Synopsis

       void ata_scsi_simulate
       struct ata_device * dev
       struct scsi_cmnd * cmd

#### Arguments

`dev`

  the target device

`cmd`

  SCSI command being sent to device.

#### Description

Interprets and directly executes a select list of SCSI commands that can be handled internally.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_sas_port_alloc
9
3.13.0-63-

### ata_sas_port_alloc

Allocate port for a SAS attached SATA device

#### Synopsis

       struct ata_port * ata_sas_port_alloc
       struct ata_host * host
       struct ata_port_info * port_info
       struct Scsi_Host * shost

#### Arguments

`host`

  ATA host container for all SAS ports

`port_info`

  Information from low-level host driver

`shost`

  SCSI host that the scsi device is attached to

#### LOCKING

PCI/etc. bus probe sem.

#### RETURNS

ata_port pointer on success / NULL on failure.

### LINUX

Kernel Hackers Manual August 2015
ata_sas_port_start
9
3.13.0-63-

### ata_sas_port_start

Set port up for dma.

#### Synopsis

       int ata_sas_port_start
       struct ata_port * ap

#### Arguments

`ap`

  Port to initialize

#### Description

Called just after data structures for each port are initialized.

May be used as the `port_start` entry in ata_port_operations.

#### LOCKING

Inherited from caller.

### LINUX

Kernel Hackers Manual August 2015
ata_sas_port_stop
9
3.13.0-63-

### ata_sas_port_stop

Undo `ata_sas_port_start`

#### Synopsis

       void ata_sas_port_stop
       struct ata_port * ap

#### Arguments

`ap`

  Port to shut down

#### Description

May be used as the `port_stop` entry in ata_port_operations.

#### LOCKING

Inherited from caller.

### LINUX

Kernel Hackers Manual August 2015
ata_sas_async_probe
9
3.13.0-63-

### ata_sas_async_probe

simply schedule probing and return

#### Synopsis

       void ata_sas_async_probe
       struct ata_port * ap

#### Arguments

`ap`

  Port to probe

#### Description

For batch scheduling of probe for sas attached ata devices, assumes the port has already been through `ata_sas_port_init`

### LINUX

Kernel Hackers Manual August 2015
ata_sas_port_init
9
3.13.0-63-

### ata_sas_port_init

Initialize a SATA device

#### Synopsis

       int ata_sas_port_init
       struct ata_port * ap

#### Arguments

`ap`

  SATA port to initialize

#### LOCKING

PCI/etc. bus probe sem.

#### RETURNS

Zero on success, non-zero on error.

### LINUX

Kernel Hackers Manual August 2015
ata_sas_port_destroy
9
3.13.0-63-

### ata_sas_port_destroy

Destroy a SATA port allocated by ata_sas_port_alloc

#### Synopsis

       void ata_sas_port_destroy
       struct ata_port * ap

#### Arguments

`ap`

  SATA port to destroy

### LINUX

Kernel Hackers Manual August 2015
ata_sas_slave_configure
9
3.13.0-63-

### ata_sas_slave_configure

Default slave_config routine for libata devices

#### Synopsis

       int ata_sas_slave_configure
       struct scsi_device * sdev
       struct ata_port * ap

#### Arguments

`sdev`

  SCSI device to configure

`ap`

  ATA port to which SCSI device is attached

#### RETURNS

Zero.

### LINUX

Kernel Hackers Manual August 2015
ata_sas_queuecmd
9
3.13.0-63-

### ata_sas_queuecmd

Issue SCSI cdb to libata-managed device

#### Synopsis

       int ata_sas_queuecmd
       struct scsi_cmnd * cmd
       struct ata_port * ap

#### Arguments

`cmd`

  SCSI command to be sent

`ap`

  ATA port to which the command is being sent

#### RETURNS

Return value from `__ata_scsi_queuecmd` if `cmd` can be queued, 0 otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_get_identity
9
3.13.0-63-

### ata_get_identity

Handler for HDIO_GET_IDENTITY ioctl

#### Synopsis

       int ata_get_identity
       struct ata_port * ap
       struct scsi_device * sdev
       void __user * arg

#### Arguments

`ap`

  target port

`sdev`

  SCSI device to get identify data for

`arg`

  User buffer area for identify data

#### LOCKING

Defined by the SCSI layer. We don't really care.

#### RETURNS

Zero on success, negative errno on error.

### LINUX

Kernel Hackers Manual August 2015
ata_cmd_ioctl
9
3.13.0-63-

### ata_cmd_ioctl

Handler for HDIO_DRIVE_CMD ioctl

#### Synopsis

       int ata_cmd_ioctl
       struct scsi_device * scsidev
       void __user * arg

#### Arguments

`scsidev`

  Device to which we are issuing command

`arg`

  User provided data for issuing command

#### LOCKING

Defined by the SCSI layer. We don't really care.

#### RETURNS

Zero on success, negative errno on error.

### LINUX

Kernel Hackers Manual August 2015
ata_task_ioctl
9
3.13.0-63-

### ata_task_ioctl

Handler for HDIO_DRIVE_TASK ioctl

#### Synopsis

       int ata_task_ioctl
       struct scsi_device * scsidev
       void __user * arg

#### Arguments

`scsidev`

  Device to which we are issuing command

`arg`

  User provided data for issuing command

#### LOCKING

Defined by the SCSI layer. We don't really care.

#### RETURNS

Zero on success, negative errno on error.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_qc_new
9
3.13.0-63-

### ata_scsi_qc_new

acquire new ata_queued_cmd reference

#### Synopsis

       struct ata_queued_cmd * ata_scsi_qc_new
       struct ata_device * dev
       struct scsi_cmnd * cmd

#### Arguments

`dev`

  ATA device to which the new command is attached

`cmd`

  SCSI command that originated this ATA command

#### Description

Obtain a reference to an unused ata_queued_cmd structure, which is the basic libata structure representing a single ATA command sent to the hardware.

If a command was available, fill in the SCSI-specific portions of the structure with information on the current command.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Command allocated, or `NULL` if none available.

### LINUX

Kernel Hackers Manual August 2015
ata_dump_status
9
3.13.0-63-

### ata_dump_status

user friendly display of error info

#### Synopsis

       void ata_dump_status
       unsigned id
       struct ata_taskfile * tf

#### Arguments

`id`

  id of the port in question

`tf`

  ptr to filled out taskfile

#### Description

Decode and dump the ATA error/status registers for the user so that they have some idea what really happened at the non make-believe layer.

#### LOCKING

inherited from caller

### LINUX

Kernel Hackers Manual August 2015
ata_to_sense_error
9
3.13.0-63-

### ata_to_sense_error

convert ATA error to SCSI error

#### Synopsis

       void ata_to_sense_error
       unsigned id
       u8 drv_stat
       u8 drv_err
       u8 * sk
       u8 * asc
       u8 * ascq
       int verbose

#### Arguments

`id`

  ATA device number

`drv_stat`

  value contained in ATA status register

`drv_err`

  value contained in ATA error register

`sk`

  the sense key we'll fill out

`asc`

  the additional sense code we'll fill out

`ascq`

  the additional sense code qualifier we'll fill out

`verbose`

  be verbose

#### Description

Converts an ATA error into a SCSI error. Fill out pointers to SK, ASC, and ASCQ bytes for later use in fixed or descriptor format sense blocks.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_gen_ata_sense
9
3.13.0-63-

### ata_gen_ata_sense

generate a SCSI fixed sense block

#### Synopsis

       void ata_gen_ata_sense
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Command that we are erroring out

#### Description

Generate sense block for a failed ATA command `qc`. Descriptor format is used to accommodate LBA48 block address.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
atapi_drain_needed
9
3.13.0-63-

### atapi_drain_needed

Check whether data transfer may overflow

#### Synopsis

       int atapi_drain_needed
       struct request * rq

#### Arguments

`rq`

  request to be checked

#### Description

ATAPI commands which transfer variable length data to host might overflow due to application error or hardare bug. This function checks whether overflow should be drained and ignored for `request`.

#### LOCKING

None.

#### RETURNS

1 if ; otherwise, 0.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_start_stop_xlat
9
3.13.0-63-

### ata_scsi_start_stop_xlat

Translate SCSI START STOP UNIT command

#### Synopsis

       unsigned int ata_scsi_start_stop_xlat
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Storage for translated ATA taskfile

#### Description

Sets up an ATA taskfile to issue STANDBY (to stop) or READ VERIFY (to start). Perhaps these commands should be preceded by CHECK POWER MODE to see what power mode the device is already in. [See SAT revision 5 at www.t10.org]

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Zero on success, non-zero on error.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_flush_xlat
9
3.13.0-63-

### ata_scsi_flush_xlat

Translate SCSI SYNCHRONIZE CACHE command

#### Synopsis

       unsigned int ata_scsi_flush_xlat
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Storage for translated ATA taskfile

#### Description

Sets up an ATA taskfile to issue FLUSH CACHE or FLUSH CACHE EXT.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Zero on success, non-zero on error.

### LINUX

Kernel Hackers Manual August 2015
scsi_6_lba_len
9
3.13.0-63-

### scsi_6_lba_len

Get LBA and transfer length

#### Synopsis

       void scsi_6_lba_len
       const u8 * cdb
       u64 * plba
       u32 * plen

#### Arguments

`cdb`

  SCSI command to translate

`plba`

  the LBA

`plen`

  the transfer length

#### Description

Calculate LBA and transfer length for 6-byte commands.

### LINUX

Kernel Hackers Manual August 2015
scsi_10_lba_len
9
3.13.0-63-

### scsi_10_lba_len

Get LBA and transfer length

#### Synopsis

       void scsi_10_lba_len
       const u8 * cdb
       u64 * plba
       u32 * plen

#### Arguments

`cdb`

  SCSI command to translate

`plba`

  the LBA

`plen`

  the transfer length

#### Description

Calculate LBA and transfer length for 10-byte commands.

### LINUX

Kernel Hackers Manual August 2015
scsi_16_lba_len
9
3.13.0-63-

### scsi_16_lba_len

Get LBA and transfer length

#### Synopsis

       void scsi_16_lba_len
       const u8 * cdb
       u64 * plba
       u32 * plen

#### Arguments

`cdb`

  SCSI command to translate

`plba`

  the LBA

`plen`

  the transfer length

#### Description

Calculate LBA and transfer length for 16-byte commands.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_verify_xlat
9
3.13.0-63-

### ata_scsi_verify_xlat

Translate SCSI VERIFY command into an ATA one

#### Synopsis

       unsigned int ata_scsi_verify_xlat
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Storage for translated ATA taskfile

#### Description

Converts SCSI VERIFY command to an ATA READ VERIFY command.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Zero on success, non-zero on error.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_rw_xlat
9
3.13.0-63-

### ata_scsi_rw_xlat

Translate SCSI r/w command into an ATA one

#### Synopsis

       unsigned int ata_scsi_rw_xlat
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Storage for translated ATA taskfile

#### Description

Converts any of six SCSI read/write commands into the ATA counterpart, including starting sector (LBA), sector count, and taking into account the device's LBA48 support.

Commands `READ_6`, `READ_10`, `READ_16`, `WRITE_6`, `WRITE_10`, and `WRITE_16` are currently supported.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Zero on success, non-zero on error.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_translate
9
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### ata_scsi_translate

Translate then issue SCSI command to ATA device

#### Synopsis

       int ata_scsi_translate
       struct ata_device * dev
       struct scsi_cmnd * cmd
       ata_xlat_func_t xlat_func

#### Arguments

`dev`

  ATA device to which the command is addressed

`cmd`

  SCSI command to execute

`xlat_func`

  Actor which translates `cmd` to an ATA taskfile

#### Description

Our ->`queuecommand` function has decided that the SCSI command issued can be directly translated into an ATA command, rather than handled internally.

This function sets up an ata_queued_cmd structure for the SCSI command, and sends that ata_queued_cmd to the hardware.

The xlat_func argument (actor) returns 0 if ready to execute ATA command, else 1 to finish translation. If 1 is returned then cmd->result (and possibly cmd->sense_buffer) are assumed to be set reflecting an error condition or clean (early) termination.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

0 on success, SCSI_ML_QUEUE_DEVICE_BUSY if the command needs to be deferred.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_rbuf_get
9
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### ata_scsi_rbuf_get

Map response buffer.

#### Synopsis

       void * ata_scsi_rbuf_get
       struct scsi_cmnd * cmd
       bool copy_in
       unsigned long * flags

#### Arguments

`cmd`

  SCSI command containing buffer to be mapped.

`copy_in`

  copy in from user buffer

`flags`

  unsigned long variable to store irq enable status

#### Description

Prepare buffer for simulated SCSI commands.

#### LOCKING

spin_lock_irqsave(ata_scsi_rbuf_lock) on success

#### RETURNS

Pointer to response buffer.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_rbuf_put
9
3.13.0-63-

### ata_scsi_rbuf_put

Unmap response buffer.

#### Synopsis

       void ata_scsi_rbuf_put
       struct scsi_cmnd * cmd
       bool copy_out
       unsigned long * flags

#### Arguments

`cmd`

  SCSI command containing buffer to be unmapped.

`copy_out`

  copy out result

`flags`

  `flags` passed to `ata_scsi_rbuf_get`

#### Description

Returns rbuf buffer. The result is copied to `cmd`'s buffer if `copy_back` is true.

#### LOCKING

Unlocks ata_scsi_rbuf_lock.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_rbuf_fill
9
3.13.0-63-

### ata_scsi_rbuf_fill

wrapper for SCSI command simulators

#### Synopsis

       void ata_scsi_rbuf_fill
       struct ata_scsi_args * args
       unsigned int (*actor)
         struct ata_scsi_args *args, u8 *rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`actor`

  Callback hook for desired SCSI command simulator

#### Description

Takes care of the hard work of simulating a SCSI command... Mapping the response buffer, calling the command's handler, and handling the handler's return value. This return value indicates whether the handler wishes the SCSI command to be completed successfully (0), or not (in which case cmd->result and sense buffer are assumed to be set).

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_inq_std
9
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### ata_scsiop_inq_std

Simulate INQUIRY command

#### Synopsis

       unsigned int ata_scsiop_inq_std
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Description

Returns standard device identification data associated with non-VPD INQUIRY command output.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_inq_00
9
3.13.0-63-

### ata_scsiop_inq_00

Simulate INQUIRY VPD page 0, list of pages

#### Synopsis

       unsigned int ata_scsiop_inq_00
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Description

Returns list of inquiry VPD pages available.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_inq_80
9
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### ata_scsiop_inq_80

Simulate INQUIRY VPD page 80, device serial number

#### Synopsis

       unsigned int ata_scsiop_inq_80
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Description

Returns ATA device serial number.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_inq_83
9
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### ata_scsiop_inq_83

Simulate INQUIRY VPD page 83, device identity

#### Synopsis

       unsigned int ata_scsiop_inq_83
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Yields two logical unit device identification designators

- vendor specific ASCII containing the ATA serial number - SAT defined t10 vendor id based containing ASCII vendor name (ATA ), model and serial numbers.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_inq_89
9
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### ata_scsiop_inq_89

Simulate INQUIRY VPD page 89, ATA info

#### Synopsis

       unsigned int ata_scsiop_inq_89
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Description

Yields SAT-specified ATA VPD page.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_noop
9
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### ata_scsiop_noop

Command handler that simply returns success.

#### Synopsis

       unsigned int ata_scsiop_noop
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Description

No operation. Simply returns success to caller, to indicate that the caller should successfully complete this SCSI command.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
modecpy
9
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### modecpy

Prepare response for MODE SENSE

#### Synopsis

       void modecpy
       u8 * dest
       const u8 * src
       int n
       bool changeable

#### Arguments

`dest`

  output buffer

`src`

  data being copied

`n`

  length of mode page

`changeable`

  whether changeable parameters are requested

#### Description

Generate a generic MODE SENSE page for either current or changeable parameters.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_msense_caching
9
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### ata_msense_caching

Simulate MODE SENSE caching info page

#### Synopsis

       unsigned int ata_msense_caching
       u16 * id
       u8 * buf
       bool changeable

#### Arguments

`id`

  device IDENTIFY data

`buf`

  output buffer

`changeable`

  whether changeable parameters are requested

#### Description

Generate a caching info page, which conditionally indicates write caching to the SCSI layer, depending on device capabilities.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_msense_ctl_mode
9
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### ata_msense_ctl_mode

Simulate MODE SENSE control mode page

#### Synopsis

       unsigned int ata_msense_ctl_mode
       u8 * buf
       bool changeable

#### Arguments

`buf`

  output buffer

`changeable`

  whether changeable parameters are requested

#### Description

Generate a generic MODE SENSE control mode page.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_msense_rw_recovery
9
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### ata_msense_rw_recovery

Simulate MODE SENSE r/w error recovery page

#### Synopsis

       unsigned int ata_msense_rw_recovery
       u8 * buf
       bool changeable

#### Arguments

`buf`

  output buffer

`changeable`

  whether changeable parameters are requested

#### Description

Generate a generic MODE SENSE r/w error recovery page.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_mode_sense
9
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### ata_scsiop_mode_sense

Simulate MODE SENSE 6, 10 commands

#### Synopsis

       unsigned int ata_scsiop_mode_sense
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Description

Simulate MODE SENSE commands. Assume this is invoked for direct access devices (e.g. disks) only. There should be no block descriptor for other device types.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_read_cap
9
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### ata_scsiop_read_cap

Simulate READ CAPACITY[ 16] commands

#### Synopsis

       unsigned int ata_scsiop_read_cap
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Description

Simulate READ CAPACITY commands.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_scsiop_report_luns
9
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### ata_scsiop_report_luns

Simulate REPORT LUNS command

#### Synopsis

       unsigned int ata_scsiop_report_luns
       struct ata_scsi_args * args
       u8 * rbuf

#### Arguments

`args`

  device IDENTIFY data / SCSI command of interest.

`rbuf`

  Response buffer, to which simulated SCSI cmd output is sent.

#### Description

Simulate REPORT LUNS command.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
atapi_xlat
9
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### atapi_xlat

Initialize PACKET taskfile

#### Synopsis

       unsigned int atapi_xlat
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  command structure to be initialized

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Zero on success, non-zero on failure.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_find_dev
9
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### ata_scsi_find_dev

lookup ata_device from scsi_cmnd

#### Synopsis

       struct ata_device * ata_scsi_find_dev
       struct ata_port * ap
       const struct scsi_device * scsidev

#### Arguments

`ap`

  ATA port to which the device is attached

`scsidev`

  SCSI device from which we derive the ATA device

#### Description

Given various information provided in struct scsi_cmnd, map that onto an ATA bus, and using that mapping determine which ata_device is associated with the SCSI command to be sent.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

Associated ATA device, or `NULL` if not found.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_pass_thru
9
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### ata_scsi_pass_thru

convert ATA pass-thru CDB to taskfile

#### Synopsis

       unsigned int ata_scsi_pass_thru
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  command structure to be initialized

#### Description

Handles either 12 or 16-byte versions of the CDB.

#### RETURNS

Zero on success, non-zero on failure.

### LINUX

Kernel Hackers Manual August 2015
ata_mselect_caching
9
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### ata_mselect_caching

Simulate MODE SELECT for caching info page

#### Synopsis

       int ata_mselect_caching
       struct ata_queued_cmd * qc
       const u8 * buf
       int len

#### Arguments

`qc`

  Storage for translated ATA taskfile

`buf`

  input buffer

`len`

  number of valid bytes in the input buffer

#### Description

Prepare a taskfile to modify caching information for the device.

#### LOCKING

None.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_mode_select_xlat
9
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### ata_scsi_mode_select_xlat

Simulate MODE SELECT 6, 10 commands

#### Synopsis

       unsigned int ata_scsi_mode_select_xlat
       struct ata_queued_cmd * qc

#### Arguments

`qc`

  Storage for translated ATA taskfile

#### Description

Converts a MODE SELECT command to an ATA SET FEATURES taskfile. Assume this is invoked for direct access devices (e.g. disks) only. There should be no block descriptor for other device types.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_get_xlat_func
9
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### ata_get_xlat_func

check if SCSI to ATA translation is possible

#### Synopsis

       ata_xlat_func_t ata_get_xlat_func
       struct ata_device * dev
       u8 cmd

#### Arguments

`dev`

  ATA device

`cmd`

  SCSI command opcode to consider

#### Description

Look up the SCSI command given, and determine whether the SCSI command is to be translated or simulated.

#### RETURNS

Pointer to translation function if possible, `NULL` if not.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_dump_cdb
9
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### ata_scsi_dump_cdb

dump SCSI command contents to dmesg

#### Synopsis

       void ata_scsi_dump_cdb
       struct ata_port * ap
       struct scsi_cmnd * cmd

#### Arguments

`ap`

  ATA port to which the command was being sent

`cmd`

  SCSI command to dump

#### Description

Prints the contents of a SCSI command via `printk`.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_offline_dev
9
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### ata_scsi_offline_dev

offline attached SCSI device

#### Synopsis

       int ata_scsi_offline_dev
       struct ata_device * dev

#### Arguments

`dev`

  ATA device to offline attached SCSI device for

#### Description

This function is called from `ata_eh_hotplug` and responsible for taking the SCSI device attached to `dev` offline. This function is called with host lock which protects dev->sdev against clearing.

#### LOCKING

spin_lock_irqsave(host lock)

#### RETURNS

1 if attached SCSI device exists, 0 otherwise.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_remove_dev
9
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### ata_scsi_remove_dev

remove attached SCSI device

#### Synopsis

       void ata_scsi_remove_dev
       struct ata_device * dev

#### Arguments

`dev`

  ATA device to remove attached SCSI device for

#### Description

This function is called from `ata_eh_scsi_hotplug` and responsible for removing the SCSI device attached to `dev`.

#### LOCKING

Kernel thread context (may sleep).

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_media_change_notify
9
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### ata_scsi_media_change_notify

send media change event

#### Synopsis

       void ata_scsi_media_change_notify
       struct ata_device * dev

#### Arguments

`dev`

  Pointer to the disk device with media change event

#### Description

Tell the block layer to send a media change notification event.

#### LOCKING

spin_lock_irqsave(host lock)

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_hotplug
9
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### ata_scsi_hotplug

SCSI part of hotplug

#### Synopsis

       void ata_scsi_hotplug
       struct work_struct * work

#### Arguments

`work`

  Pointer to ATA port to perform SCSI hotplug on

#### Description

Perform SCSI part of hotplug. It's executed from a separate workqueue after EH completes. This is necessary because SCSI hot plugging requires working EH and hot unplugging is synchronized with hot plugging with a mutex.

#### LOCKING

Kernel thread context (may sleep).

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_user_scan
9
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### ata_scsi_user_scan

indication for user-initiated bus scan

#### Synopsis

       int ata_scsi_user_scan
       struct Scsi_Host * shost
       unsigned int channel
       unsigned int id
       unsigned int lun

#### Arguments

`shost`

  SCSI host to scan

`channel`

  Channel to scan

`id`

  ID to scan

`lun`

  LUN to scan

#### Description

This function is called when user explicitly requests bus scan. Set probe pending flag and invoke EH.

#### LOCKING

SCSI layer (we don't care)

#### RETURNS

Zero.

### LINUX

Kernel Hackers Manual August 2015
ata_scsi_dev_rescan
9
3.13.0-63-

### ata_scsi_dev_rescan

initiate `scsi_rescan_device`

#### Synopsis

       void ata_scsi_dev_rescan
       struct work_struct * work

#### Arguments

`work`

  Pointer to ATA port to perform `scsi_rescan_device`

#### Description

After ATA pass thru (SAT) commands are executed successfully, libata need to propagate the changes to SCSI layer.

#### LOCKING

Kernel thread context (may sleep).

## ATA errors and exceptions

This chapter tries to identify what error/exception conditions exist for ATA/ATAPI devices and describe how they should be handled in implementation-neutral way.

The term 'error' is used to describe conditions where either an explicit error condition is reported from device or a command has timed out.

The term 'exception' is either used to describe exceptional conditions which are not errors (say, power or hotplug events), or to describe both errors and non-error exceptional conditions. Where explicit distinction between error and exception is necessary, the term 'non-error exception' is used.

### Exception categories

Exceptions are described primarily with respect to legacy taskfile + bus master IDE interface. If a controller provides other better mechanism for error reporting, mapping those into categories described below shouldn't be difficult.

In the following sections, two recovery actions - reset and reconfiguring transport - are mentioned. These are described further in .

#### HSM violation

This error is indicated when STATUS value doesn't match HSM requirement during issuing or execution any ATA/ATAPI command.

##### Examples

- ATA_STATUS doesn't contain !BSY && DRDY && !DRQ while trying to issue a command.

- !BSY && !DRQ during PIO data transfer.

- DRQ on command completion.

- !BSY && ERR after CDB transfer starts but before the last byte of CDB is transferred. ATA/ATAPI standard states that "The device shall not terminate the PACKET command with an error before the last byte of the command packet has been written" in the error outputs description of PACKET command and the state diagram doesn't include such transitions.

In these cases, HSM is violated and not much information regarding the error can be acquired from STATUS or ERROR register. IOW, this error can be anything - driver bug, faulty device, controller and/or cable.

As HSM is violated, reset is necessary to restore known state. Reconfiguring transport for lower speed might be helpful too as transmission errors sometimes cause this kind of errors.

#### ATA/ATAPI device error (non-NCQ / non-CHECK CONDITION)

These are errors detected and reported by ATA/ATAPI devices indicating device problems. For this type of errors, STATUS and ERROR register values are valid and describe error condition. Note that some of ATA bus errors are detected by ATA/ATAPI devices and reported using the same mechanism as device errors. Those cases are described later in this section.

For ATA commands, this type of errors are indicated by !BSY && ERR during command execution and on completion.

For ATAPI commands,

- !BSY && ERR && ABRT right after issuing PACKET indicates that PACKET command is not supported and falls in this category.

- !BSY && ERR(==CHK) && !ABRT after the last byte of CDB is transferred indicates CHECK CONDITION and doesn't fall in this category.

- !BSY && ERR(==CHK) && ABRT after the last byte of CDB is transferred *probably* indicates CHECK CONDITION and doesn't fall in this category.

Of errors detected as above, the followings are not ATA/ATAPI device errors but ATA bus errors and should be handled according to .

CRC error during data transfer

  This is indicated by ICRC bit in the ERROR register and means that corruption occurred during data transfer. Up to ATA/ATAPI-7, the standard specifies that this bit is only applicable to UDMA transfers but ATA/ATAPI-8 draft revision 1f says that the bit may be applicable to multiword DMA and PIO.

ABRT error during data transfer or on completion

  Up to ATA/ATAPI-7, the standard specifies that ABRT could be set on ICRC errors and on cases where a device is not able to complete a command. Combined with the fact that MWDMA and PIO transfer errors aren't allowed to use ICRC bit up to ATA/ATAPI-7, it seems to imply that ABRT bit alone could indicate transfer errors.

  However, ATA/ATAPI-8 draft revision 1f removes the part that ICRC errors can turn on ABRT. So, this is kind of gray area. Some heuristics are needed here.

ATA/ATAPI device errors can be further categorized as follows.

Media errors

  This is indicated by UNC bit in the ERROR register. ATA devices reports UNC error only after certain number of retries cannot recover the data, so there's nothing much else to do other than notifying upper layer.

  READ and WRITE commands report CHS or LBA of the first failed sector but ATA/ATAPI standard specifies that the amount of transferred data on error completion is indeterminate, so we cannot assume that sectors preceding the failed sector have been transferred and thus cannot complete those sectors successfully as SCSI does.

Media changed / media change requested error

  <<TODO: fill here>>

Address error

  This is indicated by IDNF bit in the ERROR register. Report to upper layer.

Other errors

  This can be invalid command or parameter indicated by ABRT ERROR bit or some other error condition. Note that ABRT bit can indicate a lot of things including ICRC and Address errors. Heuristics needed.

Depending on commands, not all STATUS/ERROR bits are applicable. These non-applicable bits are marked with "na" in the output descriptions but up to ATA/ATAPI-7 no definition of "na" can be found. However, ATA/ATAPI-8 draft revision 1f describes "N/A" as follows.

> 3.2.3.3a N/A

>   A keyword the indicates a field has no defined value in this standard and should not be checked by the host or device. N/A fields should be cleared to zero.

So, it seems reasonable to assume that "na" bits are cleared to zero by devices and thus need no explicit masking.

#### ATAPI device CHECK CONDITION

ATAPI device CHECK CONDITION error is indicated by set CHK bit (ERR bit) in the STATUS register after the last byte of CDB is transferred for a PACKET command. For this kind of errors, sense data should be acquired to gather information regarding the errors. REQUEST SENSE packet command should be used to acquire sense data.

Once sense data is acquired, this type of errors can be handled similary to other SCSI errors. Note that sense data may indicate ATA bus error (e.g. Sense Key 04h HARDWARE ERROR && ASC/ASCQ 47h/00h SCSI PARITY ERROR). In such cases, the error should be considered as an ATA bus error and handled according to .

#### ATA device error (NCQ)

NCQ command error is indicated by cleared BSY and set ERR bit during NCQ command phase (one or more NCQ commands outstanding). Although STATUS and ERROR registers will contain valid values describing the error, READ LOG EXT is required to clear the error condition, determine which command has failed and acquire more information.

READ LOG EXT Log Page 10h reports which tag has failed and taskfile register values describing the error. With this information the failed command can be handled as a normal ATA command error as in and all other in-flight commands must be retried. Note that this retry should not be counted - it's likely that commands retried this way would have completed normally if it were not for the failed command.

Note that ATA bus errors can be reported as ATA device NCQ errors. This should be handled as described in .

If READ LOG EXT Log Page 10h fails or reports NQ, we're thoroughly screwed. This condition should be treated according to .

#### ATA bus error

ATA bus error means that data corruption occurred during transmission over ATA bus (SATA or PATA). This type of errors can be indicated by

- ICRC or ABRT error as described in .

- Controller-specific error completion with error information indicating transmission error.

- On some controllers, command timeout. In this case, there may be a mechanism to determine that the timeout is due to transmission error.

- Unknown/random errors, timeouts and all sorts of weirdities.

As described above, transmission errors can cause wide variety of symptoms ranging from device ICRC error to random device lockup, and, for many cases, there is no way to tell if an error condition is due to transmission error or not; therefore, it's necessary to employ some kind of heuristic when dealing with errors and timeouts. For example, encountering repetitive ABRT errors for known supported command is likely to indicate ATA bus error.

Once it's determined that ATA bus errors have possibly occurred, lowering ATA bus transmission speed is one of actions which may alleviate the problem. See for more information.

#### PCI bus error

Data corruption or other failures during transmission over PCI (or other system bus). For standard BMDMA, this is indicated by Error bit in the BMDMA Status register. This type of errors must be logged as it indicates something is very wrong with the system. Resetting host controller is recommended.

#### Late completion

This occurs when timeout occurs and the timeout handler finds out that the timed out command has completed successfully or with error. This is usually caused by lost interrupts. This type of errors must be logged. Resetting host controller is recommended.

#### Unknown error (timeout)

This is when timeout occurs and the command is still processing or the host and device are in unknown state. When this occurs, HSM could be in any valid or invalid state. To bring the device to known state and make it forget about the timed out command, resetting is necessary. The timed out command may be retried.

Timeouts can also be caused by transmission errors. Refer to for more details.

#### Hotplug and power management exceptions

<<TODO: fill here>>

### EH recovery actions

This section discusses several important recovery actions.

#### Clearing error condition

Many controllers require its error registers to be cleared by error handler. Different controllers may have different requirements.

For SATA, it's strongly recommended to clear at least SError register during error handling.

#### Reset

During EH, resetting is necessary in the following cases.

- HSM is in unknown or invalid state

- HBA is in unknown or invalid state

- EH needs to make HBA/device forget about in-flight commands

- HBA/device behaves weirdly

Resetting during EH might be a good idea regardless of error condition to improve EH robustness. Whether to reset both or either one of HBA and device depends on situation but the following scheme is recommended.

- When it's known that HBA is in ready state but ATA/ATAPI device is in unknown state, reset only device.

- If HBA is in unknown state, reset both HBA and device.

HBA resetting is implementation specific. For a controller complying to taskfile/BMDMA PCI IDE, stopping active DMA transaction may be sufficient iff BMDMA state is the only HBA context. But even mostly taskfile/BMDMA PCI IDE complying controllers may have implementation specific requirements and mechanism to reset themselves. This must be addressed by specific drivers.

OTOH, ATA/ATAPI standard describes in detail ways to reset ATA/ATAPI devices.

PATA hardware reset

  This is hardware initiated device reset signalled with asserted PATA RESET- signal. There is no standard way to initiate hardware reset from software although some hardware provides registers that allow driver to directly tweak the RESET- signal.

Software reset

  This is achieved by turning CONTROL SRST bit on for at least 5us. Both PATA and SATA support it but, in case of SATA, this may require controller-specific support as the second Register FIS to clear SRST should be transmitted while BSY bit is still set. Note that on PATA, this resets both master and slave devices on a channel.

EXECUTE DEVICE DIAGNOSTIC command

  Although ATA/ATAPI standard doesn't describe exactly, EDD implies some level of resetting, possibly similar level with software reset. Host-side EDD protocol can be handled with normal command processing and most SATA controllers should be able to handle EDD's just like other commands. As in software reset, EDD affects both devices on a PATA bus.

  Although EDD does reset devices, this doesn't suit error handling as EDD cannot be issued while BSY is set and it's unclear how it will act when device is in unknown/weird state.

ATAPI DEVICE RESET command

  This is very similar to software reset except that reset can be restricted to the selected device without affecting the other device sharing the cable.

SATA phy reset

  This is the preferred way of resetting a SATA device. In effect, it's identical to PATA hardware reset. Note that this can be done with the standard SCR Control register. As such, it's usually easier to implement than software reset.

One more thing to consider when resetting devices is that resetting clears certain configuration parameters and they need to be set to their previous or newly adjusted values after reset.

Parameters affected are.

- CHS set up with INITIALIZE DEVICE PARAMETERS (seldom used)

- Parameters set with SET FEATURES including transfer mode setting

- Block count set with SET MULTIPLE MODE

- Other parameters (SET MAX, MEDIA LOCK...)

ATA/ATAPI standard specifies that some parameters must be maintained across hardware or software reset, but doesn't strictly specify all of them. Always reconfiguring needed parameters after reset is required for robustness. Note that this also applies when resuming from deep sleep (power-off).

Also, ATA/ATAPI standard requires that IDENTIFY DEVICE / IDENTIFY PACKET DEVICE is issued after any configuration parameter is updated or a hardware reset and the result used for further operation. OS driver is required to implement revalidation mechanism to support this.

#### Reconfigure transport

For both PATA and SATA, a lot of corners are cut for cheap connectors, cables or controllers and it's quite common to see high transmission error rate. This can be mitigated by lowering transmission speed.

The following is a possible scheme Jeff Garzik suggested.

> If more than $N (3?) transmission errors happen in 15 minutes,

> - if SATA, decrease SATA PHY speed. if speed cannot be decreased,

> - decrease UDMA xfer speed. if at UDMA0, switch to PIO4,

> - decrease PIO xfer speed. if at PIO3, complain, but continue

## ata_piix Internals

### LINUX

Kernel Hackers Manual August 2015
ich_pata_cable_detect
9
3.13.0-63-

### ich_pata_cable_detect

Probe host controller cable detect info

#### Synopsis

       int ich_pata_cable_detect
       struct ata_port * ap

#### Arguments

`ap`

  Port for which cable detect info is desired

#### Description

Read 80c cable indicator from ATA PCI device's PCI config register. This register is normally set by firmware (BIOS).

#### LOCKING

None (inherited from caller).

### LINUX

Kernel Hackers Manual August 2015
piix_pata_prereset
9
3.13.0-63-

### piix_pata_prereset

prereset for PATA host controller

#### Synopsis

       int piix_pata_prereset
       struct ata_link * link
       unsigned long deadline

#### Arguments

`link`

  Target link

`deadline`

  deadline jiffies for the operation

#### LOCKING

None (inherited from caller).

### LINUX

Kernel Hackers Manual August 2015
piix_set_piomode
9
3.13.0-63-

### piix_set_piomode

Initialize host controller PATA PIO timings

#### Synopsis

       void piix_set_piomode
       struct ata_port * ap
       struct ata_device * adev

#### Arguments

`ap`

  Port whose timings we are configuring

`adev`

  Drive in question

#### Description

Set PIO mode for device, in host controller PCI config space.

#### LOCKING

None (inherited from caller).

### LINUX

Kernel Hackers Manual August 2015
do_pata_set_dmamode
9
3.13.0-63-

### do_pata_set_dmamode

Initialize host controller PATA PIO timings

#### Synopsis

       void do_pata_set_dmamode
       struct ata_port * ap
       struct ata_device * adev
       int isich

#### Arguments

`ap`

  Port whose timings we are configuring

`adev`

  Drive in question

`isich`

  set if the chip is an ICH device

#### Description

Set UDMA mode for device, in host controller PCI config space.

#### LOCKING

None (inherited from caller).

### LINUX

Kernel Hackers Manual August 2015
piix_set_dmamode
9
3.13.0-63-

### piix_set_dmamode

Initialize host controller PATA DMA timings

#### Synopsis

       void piix_set_dmamode
       struct ata_port * ap
       struct ata_device * adev

#### Arguments

`ap`

  Port whose timings we are configuring

`adev`

  um

#### Description

Set MW/UDMA mode for device, in host controller PCI config space.

#### LOCKING

None (inherited from caller).

### LINUX

Kernel Hackers Manual August 2015
ich_set_dmamode
9
3.13.0-63-

### ich_set_dmamode

Initialize host controller PATA DMA timings

#### Synopsis

       void ich_set_dmamode
       struct ata_port * ap
       struct ata_device * adev

#### Arguments

`ap`

  Port whose timings we are configuring

`adev`

  um

#### Description

Set MW/UDMA mode for device, in host controller PCI config space.

#### LOCKING

None (inherited from caller).

### LINUX

Kernel Hackers Manual August 2015
piix_check_450nx_errata
9
3.13.0-63-

### piix_check_450nx_errata

Check for problem 450NX setup

#### Synopsis

       int piix_check_450nx_errata
       struct pci_dev * ata_dev

#### Arguments

`ata_dev`

  the PCI device to check

#### Description

Check for the present of 450NX errata #19 and errata #25. If they are found return an error code so we can turn off DMA

### LINUX

Kernel Hackers Manual August 2015
piix_init_one
9
3.13.0-63-

### piix_init_one

Register PIIX ATA PCI device with kernel services

#### Synopsis

       int piix_init_one
       struct pci_dev * pdev
       const struct pci_device_id * ent

#### Arguments

`pdev`

  PCI device to register

`ent`

  Entry in piix_pci_tbl matching with `pdev`

#### Description

Called from kernel PCI layer. We probe for combined mode (sigh), and then hand over control to libata, for it to do the rest.

#### LOCKING

Inherited from PCI layer (may sleep).

#### RETURNS

Zero on success, or -ERRNO value.

## sata_sil Internals

### LINUX

Kernel Hackers Manual August 2015
sil_set_mode
9
3.13.0-63-

### sil_set_mode

wrap set_mode functions

#### Synopsis

       int sil_set_mode
       struct ata_link * link
       struct ata_device ** r_failed

#### Arguments

`link`

  link to set up

`r_failed`

  returned device when we fail

#### Description

Wrap the libata method for device setup as after the setup we need to inspect the results and do some configuration work

### LINUX

Kernel Hackers Manual August 2015
sil_dev_config
9
3.13.0-63-

### sil_dev_config

Apply device/host-specific errata fixups

#### Synopsis

       void sil_dev_config
       struct ata_device * dev

#### Arguments

`dev`

  Device to be examined

#### Description

After the IDENTIFY [PACKET] DEVICE step is complete, and a device is known to be present, this function is called. We apply two errata fixups which are specific to Silicon Image, a Seagate and a Maxtor fixup.

For certain Seagate devices, we must limit the maximum sectors to under 8K.

For certain Maxtor devices, we must not program the drive beyond udma5.

Both fixups are unfairly pessimistic. As soon as I get more information on these errata, I will create a more exhaustive list, and apply the fixups to only the specific devices/hosts/firmwares that need it.

20040111 - Seagate drives affected by the Mod15Write bug are blacklisted The Maxtor quirk is in the blacklist, but I'm keeping the original pessimistic fix for the following reasons... - There seems to be less info on it, only one device gleaned off the Windows driver, maybe only one is affected. More info would be greatly appreciated. - But then again UDMA5 is hardly anything to complain about

## Thanks

The bulk of the ATA knowledge comes thanks to long conversations with Andre Hedrick (www.linux-ide.org), and long hours pondering the ATA and SCSI specifications.

Thanks to Alan Cox for pointing out similarities between SATA and SCSI, and in general for motivation to hack on libata.

libata's device detection method, ata_pio_devchk, and in general all the early probing was based on extensive study of Hale Landis's probe/reset code in his ATADRVR driver (www.ata-atapi.com).