1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _VIDIOC_G_EDID:
5
6 ******************************************************************************
7 ioctl VIDIOC_G_EDID, VIDIOC_S_EDID, VIDIOC_SUBDEV_G_EDID, VIDIOC_SUBDEV_S_EDID
8 ******************************************************************************
9
10 Name
11 ====
12
13 VIDIOC_G_EDID - VIDIOC_S_EDID - VIDIOC_SUBDEV_G_EDID - VIDIOC_SUBDEV_S_EDID - Get or set the EDID of a video receiver/transmitter
14
15 Synopsis
16 ========
17
18 .. c:macro:: VIDIOC_G_EDID
19
20 ``int ioctl(int fd, VIDIOC_G_EDID, struct v4l2_edid *argp)``
21
22 .. c:macro:: VIDIOC_S_EDID
23
24 ``int ioctl(int fd, VIDIOC_S_EDID, struct v4l2_edid *argp)``
25
26 .. c:macro:: VIDIOC_SUBDEV_G_EDID
27
28 ``int ioctl(int fd, VIDIOC_SUBDEV_G_EDID, struct v4l2_edid *argp)``
29
30 .. c:macro:: VIDIOC_SUBDEV_S_EDID
31
32 ``int ioctl(int fd, VIDIOC_SUBDEV_S_EDID, struct v4l2_edid *argp)``
33
34 Arguments
35 =========
36
37 ``fd``
38 File descriptor returned by :c:func:`open()`.
39
40 ``argp``
41 Pointer to struct :c:type:`v4l2_edid`.
42
43 Description
44 ===========
45
46 These ioctls can be used to get or set an EDID associated with an input
47 from a receiver or an output of a transmitter device. They can be used
48 with subdevice nodes (/dev/v4l-subdevX) or with video nodes
49 (/dev/videoX).
50
51 When used with video nodes the ``pad`` field represents the input (for
52 video capture devices) or output (for video output devices) index as is
53 returned by :ref:`VIDIOC_ENUMINPUT` and
54 :ref:`VIDIOC_ENUMOUTPUT` respectively. When used
55 with subdevice nodes the ``pad`` field represents the input or output
56 pad of the subdevice. If there is no EDID support for the given ``pad``
57 value, then the ``EINVAL`` error code will be returned.
58
59 To get the EDID data the application has to fill in the ``pad``,
60 ``start_block``, ``blocks`` and ``edid`` fields, zero the ``reserved``
61 array and call :ref:`VIDIOC_G_EDID <VIDIOC_G_EDID>`. The current EDID from block
62 ``start_block`` and of size ``blocks`` will be placed in the memory
63 ``edid`` points to. The ``edid`` pointer must point to memory at least
64 ``blocks`` * 128 bytes large (the size of one block is 128 bytes).
65
66 If there are fewer blocks than specified, then the driver will set
67 ``blocks`` to the actual number of blocks. If there are no EDID blocks
68 available at all, then the error code ``ENODATA`` is set.
69
70 If blocks have to be retrieved from the sink, then this call will block
71 until they have been read.
72
73 If ``start_block`` and ``blocks`` are both set to 0 when
74 :ref:`VIDIOC_G_EDID <VIDIOC_G_EDID>` is called, then the driver will set ``blocks`` to the
75 total number of available EDID blocks and it will return 0 without
76 copying any data. This is an easy way to discover how many EDID blocks
77 there are.
78
79 .. note::
80
81 If there are no EDID blocks available at all, then
82 the driver will set ``blocks`` to 0 and it returns 0.
83
84 To set the EDID blocks of a receiver the application has to fill in the
85 ``pad``, ``blocks`` and ``edid`` fields, set ``start_block`` to 0 and
86 zero the ``reserved`` array. It is not possible to set part of an EDID,
87 it is always all or nothing. Setting the EDID data is only valid for
88 receivers as it makes no sense for a transmitter.
89
90 The driver assumes that the full EDID is passed in. If there are more
91 EDID blocks than the hardware can handle then the EDID is not written,
92 but instead the error code ``E2BIG`` is set and ``blocks`` is set to the
93 maximum that the hardware supports. If ``start_block`` is any value
94 other than 0 then the error code ``EINVAL`` is set.
95
96 To disable an EDID you set ``blocks`` to 0. Depending on the hardware
97 this will drive the hotplug pin low and/or block the source from reading
98 the EDID data in some way. In any case, the end result is the same: the
99 EDID is no longer available.
100
101 .. c:type:: v4l2_edid
102
103 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
104
105 .. flat-table:: struct v4l2_edid
106 :header-rows: 0
107 :stub-columns: 0
108 :widths: 1 1 2
109
110 * - __u32
111 - ``pad``
112 - Pad for which to get/set the EDID blocks. When used with a video
113 device node the pad represents the input or output index as
114 returned by :ref:`VIDIOC_ENUMINPUT` and
115 :ref:`VIDIOC_ENUMOUTPUT` respectively.
116 * - __u32
117 - ``start_block``
118 - Read the EDID from starting with this block. Must be 0 when
119 setting the EDID.
120 * - __u32
121 - ``blocks``
122 - The number of blocks to get or set. Must be less or equal to 256
123 (the maximum number of blocks as defined by the standard). When
124 you set the EDID and ``blocks`` is 0, then the EDID is disabled or
125 erased.
126 * - __u32
127 - ``reserved``\ [5]
128 - Reserved for future extensions. Applications and drivers must set
129 the array to zero.
130 * - __u8 *
131 - ``edid``
132 - Pointer to memory that contains the EDID. The minimum size is
133 ``blocks`` * 128.
134
135 Return Value
136 ============
137
138 On success 0 is returned, on error -1 and the ``errno`` variable is set
139 appropriately. The generic error codes are described at the
140 :ref:`Generic Error Codes <gen-errors>` chapter.
141
142 ``ENODATA``
143 The EDID data is not available.
144
145 ``E2BIG``
146 The EDID data you provided is more than the hardware can handle.
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