7.27. ioctl VIDIOC_G_EDID, VIDIOC_S_EDID, VIDIOC_SUBDEV_G_EDID, VIDIOC_SUBDEV_S_EDID¶
VIDIOC_G_EDID - VIDIOC_S_EDID - VIDIOC_SUBDEV_G_EDID - VIDIOC_SUBDEV_S_EDID - Get or set the EDID of a video receiver/transmitter
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 ioctl VIDIOC_ENUMINPUT and
ioctl 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
value, then the
EINVAL error code will be returned.
To get the EDID data the application has to fill in the
edid fields, zero the
array 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.
blocks are both set to 0 when
VIDIOC_G_EDID is called, then the driver will set
blocks to the
total number of available EDID blocks and it will return 0 without
copying any data. This is an easy way to discover how many EDID blocks
If there are no EDID blocks available at all, then
the driver will set
blocks to 0 and it returns 0.
To set the EDID blocks of a receiver the application has to fill in the
edid fields, set
start_block to 0 and
reserved array. 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.
||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 ioctl VIDIOC_ENUMINPUT and ioctl VIDIOC_ENUMOUTPUT respectively.|
||Read the EDID from starting with this block. Must be 0 when setting the EDID.|
||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
||Reserved for future extensions. Applications and drivers must set the array to zero.|
||Pointer to memory that contains the EDID. The minimum size is