VIDIOC_G_EDID, VIDIOC_S_EDID — Get or set the EDID of a video receiver/transmitter
int ioctl( | int fd, |
| int request, | |
struct v4l2_edid *argp); |
int ioctl( | int fd, |
| int request, | |
struct v4l2_edid *argp); |
These ioctls can be used to get or set an EDID associated with an input from a receiver or an output of a transmitter device. They can be used with subdevice nodes (/dev/v4l-subdevX) or with video nodes (/dev/videoX).
When used with video nodes the pad field represents the
input (for video capture devices) or output (for video output devices) index as
is returned by VIDIOC_ENUMINPUT and VIDIOC_ENUMOUTPUT respectively. When used
with subdevice nodes the pad field represents the
input or output pad of the subdevice. If there is no EDID support for the given
pad value, then the EINVAL error code will be returned.
To get the EDID data the application has to fill in the pad,
start_block, blocks and edid
fields and call VIDIOC_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.62. struct v4l2_edid
| __u32 | pad | Pad for which to get/set the EDID blocks. When used with a video device
node the pad represents the input or output index as returned by
VIDIOC_ENUMINPUT and VIDIOC_ENUMOUTPUT respectively. |
| __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. |
| __u32 | reserved[5] | Reserved for future extensions. Applications and drivers must set the array to zero. |
| __u8 * | edid | Pointer to memory that contains the EDID. The minimum size is
blocks * 128. |
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.
The EDID data is not available.
The EDID data you provided is more than the hardware can handle.