147 lines
5.0 KiB
ReStructuredText
147 lines
5.0 KiB
ReStructuredText
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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. c:namespace:: V4L
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.. _VIDIOC_G_EDID:
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******************************************************************************
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ioctl VIDIOC_G_EDID, VIDIOC_S_EDID, VIDIOC_SUBDEV_G_EDID, VIDIOC_SUBDEV_S_EDID
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******************************************************************************
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Name
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====
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VIDIOC_G_EDID - VIDIOC_S_EDID - VIDIOC_SUBDEV_G_EDID - VIDIOC_SUBDEV_S_EDID - Get or set the EDID of a video receiver/transmitter
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Synopsis
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========
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.. c:macro:: VIDIOC_G_EDID
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``int ioctl(int fd, VIDIOC_G_EDID, struct v4l2_edid *argp)``
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.. c:macro:: VIDIOC_S_EDID
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``int ioctl(int fd, VIDIOC_S_EDID, struct v4l2_edid *argp)``
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.. c:macro:: VIDIOC_SUBDEV_G_EDID
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``int ioctl(int fd, VIDIOC_SUBDEV_G_EDID, struct v4l2_edid *argp)``
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.. c:macro:: VIDIOC_SUBDEV_S_EDID
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``int ioctl(int fd, VIDIOC_SUBDEV_S_EDID, struct v4l2_edid *argp)``
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Arguments
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=========
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``fd``
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File descriptor returned by :c:func:`open()`.
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``argp``
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Pointer to struct :c:type:`v4l2_edid`.
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Description
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===========
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These ioctls can be used to get or set an EDID associated with an input
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from a receiver or an output of a transmitter device. They can be used
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with subdevice nodes (/dev/v4l-subdevX) or with video nodes
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(/dev/videoX).
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When used with video nodes the ``pad`` field represents the input (for
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video capture devices) or output (for video output devices) index as is
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returned by :ref:`VIDIOC_ENUMINPUT` and
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:ref:`VIDIOC_ENUMOUTPUT` respectively. When used
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with subdevice nodes the ``pad`` field represents the input or output
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pad of the subdevice. If there is no EDID support for the given ``pad``
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value, then the ``EINVAL`` error code will be returned.
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To get the EDID data the application has to fill in the ``pad``,
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``start_block``, ``blocks`` and ``edid`` fields, zero the ``reserved``
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array and call :ref:`VIDIOC_G_EDID <VIDIOC_G_EDID>`. The current EDID from block
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``start_block`` and of size ``blocks`` will be placed in the memory
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``edid`` points to. The ``edid`` pointer must point to memory at least
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``blocks`` * 128 bytes large (the size of one block is 128 bytes).
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If there are fewer blocks than specified, then the driver will set
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``blocks`` to the actual number of blocks. If there are no EDID blocks
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available at all, then the error code ``ENODATA`` is set.
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If blocks have to be retrieved from the sink, then this call will block
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until they have been read.
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If ``start_block`` and ``blocks`` are both set to 0 when
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:ref:`VIDIOC_G_EDID <VIDIOC_G_EDID>` is called, then the driver will set ``blocks`` to the
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total number of available EDID blocks and it will return 0 without
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copying any data. This is an easy way to discover how many EDID blocks
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there are.
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.. note::
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If there are no EDID blocks available at all, then
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the driver will set ``blocks`` to 0 and it returns 0.
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To set the EDID blocks of a receiver the application has to fill in the
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``pad``, ``blocks`` and ``edid`` fields, set ``start_block`` to 0 and
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zero the ``reserved`` array. It is not possible to set part of an EDID,
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it is always all or nothing. Setting the EDID data is only valid for
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receivers as it makes no sense for a transmitter.
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The driver assumes that the full EDID is passed in. If there are more
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EDID blocks than the hardware can handle then the EDID is not written,
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but instead the error code ``E2BIG`` is set and ``blocks`` is set to the
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maximum that the hardware supports. If ``start_block`` is any value
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other than 0 then the error code ``EINVAL`` is set.
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To disable an EDID you set ``blocks`` to 0. Depending on the hardware
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this will drive the hotplug pin low and/or block the source from reading
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the EDID data in some way. In any case, the end result is the same: the
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EDID is no longer available.
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.. c:type:: v4l2_edid
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
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.. flat-table:: struct v4l2_edid
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 2
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* - __u32
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- ``pad``
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- Pad for which to get/set the EDID blocks. When used with a video
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device node the pad represents the input or output index as
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returned by :ref:`VIDIOC_ENUMINPUT` and
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:ref:`VIDIOC_ENUMOUTPUT` respectively.
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* - __u32
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- ``start_block``
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- Read the EDID from starting with this block. Must be 0 when
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setting the EDID.
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* - __u32
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- ``blocks``
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- The number of blocks to get or set. Must be less or equal to 256
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(the maximum number of blocks as defined by the standard). When
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you set the EDID and ``blocks`` is 0, then the EDID is disabled or
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erased.
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* - __u32
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- ``reserved``\ [5]
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- Reserved for future extensions. Applications and drivers must set
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the array to zero.
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* - __u8 *
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- ``edid``
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- Pointer to memory that contains the EDID. The minimum size is
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``blocks`` * 128.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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``ENODATA``
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The EDID data is not available.
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``E2BIG``
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The EDID data you provided is more than the hardware can handle.
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