ioctl VIDIOC_SUBDEV_G_EDID, VIDIOC_SUBDEV_S_EDID
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## Name

VIDIOC_SUBDEV_G_EDID, VIDIOC_SUBDEV_S_EDID — Get or set the EDID of a video receiver/transmitter

## Synopsis

`int ioctl(` | int fd,
| int request,
| struct v4l2_subdev_edid *argp`)`;

`int ioctl(` | int fd,
| int request,
| const struct v4l2_subdev_edid *argp`)`;

## Arguments

`fd`

  File descriptor returned by `open()`.

`request`

  VIDIOC_SUBDEV_G_EDID, VIDIOC_SUBDEV_S_EDID

`argp`

## Description

These ioctls can be used to get or set an EDID associated with an input pad from a receiver or an output pad of a transmitter subdevice.

To get the EDID data the application has to fill in the `pad`, `start_block`, `blocks` and `edid` fields and call `VIDIOC_SUBDEV_G_EDID`. The current EDID from block `start_block` and of size `blocks` will be placed in the memory `edid` points to. The `edid` pointer must point to memory at least `blocks` * 128 bytes large (the size of one block is 128 bytes).

If there are fewer blocks than specified, then the driver will set `blocks` to the actual number of blocks. If there are no EDID blocks available at all, then the error code ENODATA is set.

If blocks have to be retrieved from the sink, then this call will block until they have been read.

To set the EDID blocks of a receiver the application has to fill in the `pad`, `blocks` and `edid` fields and set `start_block` to 0. It is not possible to set part of an EDID, it is always all or nothing. Setting the EDID data is only valid for receivers as it makes no sense for a transmitter.

The driver assumes that the full EDID is passed in. If there are more EDID blocks than the hardware can handle then the EDID is not written, but instead the error code E2BIG is set and `blocks` is set to the maximum that the hardware supports. If `start_block` is any value other than 0 then the error code EINVAL is set.

To disable an EDID you set `blocks` to 0. Depending on the hardware this will drive the hotplug pin low and/or block the source from reading the EDID data in some way. In any case, the end result is the same: the EDID is no longer available.

Table A.100. struct v4l2_subdev_edid

__u32 | `pad` | Pad for which to get/set the EDID blocks.
__u32 | `start_block` | Read the EDID from starting with this block. Must be 0 when setting the EDID.
__u32 | `blocks` | The number of blocks to get or set. Must be less or equal to 256 (the maximum number of blocks as defined by the standard). When you set the EDID and `blocks` is 0, then the EDID is disabled or erased.
__u8 * | `edid` | Pointer to memory that contains the EDID. The minimum size is `blocks` * 128.
__u32 | `reserved`[5] | Reserved for future extensions. Applications and drivers must set the array to zero.

## Return Value

On success 0 is returned, on error -1 and the `errno` variable is set appropriately. The generic error codes are described at the Generic Error Codes chapter.

ENODATA

  The EDID data is not available.

E2BIG

  The EDID data you provided is more than the hardware can handle.

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