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diff --git a/Documentation/media/uapi/v4l/vidioc-g-edid.rst b/Documentation/media/uapi/v4l/vidioc-g-edid.rst new file mode 100644 index 000000000000..907b2c1764a3 --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-g-edid.rst @@ -0,0 +1,158 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _VIDIOC_G_EDID: + +****************************************************************************** +ioctl VIDIOC_G_EDID, VIDIOC_S_EDID, VIDIOC_SUBDEV_G_EDID, VIDIOC_SUBDEV_S_EDID +****************************************************************************** + +Name +==== + +VIDIOC_G_EDID - VIDIOC_S_EDID - VIDIOC_SUBDEV_G_EDID - VIDIOC_SUBDEV_S_EDID - Get or set the EDID of a video receiver/transmitter + + +Synopsis +======== + +.. cpp:function:: int ioctl( int fd, int request, struct v4l2_edid *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <func-open>`. + +``request`` + VIDIOC_G_EDID, VIDIOC_S_EDID, 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 +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 :ref:`VIDIOC_ENUMINPUT` and +:ref:`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, zero the ``reserved`` +array and call :ref:`VIDIOC_G_EDID <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. + +If ``start_block`` and ``blocks`` are both set to 0 when +:ref:`VIDIOC_G_EDID <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 +there are. Note that 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 +``pad``, ``blocks`` and ``edid`` fields, set ``start_block`` to 0 and +zero the ``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. + + +.. _v4l2-edid: + +.. flat-table:: struct v4l2_edid + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - __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 :ref:`VIDIOC_ENUMINPUT` and + :ref:`VIDIOC_ENUMOUTPUT` respectively. + + - .. row 2 + + - __u32 + + - ``start_block`` + + - Read the EDID from starting with this block. Must be 0 when + setting the EDID. + + - .. row 3 + + - __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. + + - .. row 4 + + - __u32 + + - ``reserved``\ [5] + + - Reserved for future extensions. Applications and drivers must set + the array to zero. + + - .. row 5 + + - __u8 * + + - ``edid`` + + - Pointer to memory that contains the EDID. The minimum size is + ``blocks`` * 128. + + +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 +:ref:`Generic Error Codes <gen-errors>` chapter. + +``ENODATA`` + The EDID data is not available. + +``E2BIG`` + The EDID data you provided is more than the hardware can handle. |