1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L 2 .. c:namespace:: V4L
3 3
4 .. _VIDIOC_QUERY_DV_TIMINGS: 4 .. _VIDIOC_QUERY_DV_TIMINGS:
5 5
6 ***************************** 6 *****************************
7 ioctl VIDIOC_QUERY_DV_TIMINGS 7 ioctl VIDIOC_QUERY_DV_TIMINGS
8 ***************************** 8 *****************************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 VIDIOC_QUERY_DV_TIMINGS - VIDIOC_SUBDEV_QUERY_ 13 VIDIOC_QUERY_DV_TIMINGS - VIDIOC_SUBDEV_QUERY_DV_TIMINGS - Sense the DV preset received by the current input
14 14
15 Synopsis 15 Synopsis
16 ======== 16 ========
17 17
18 .. c:macro:: VIDIOC_QUERY_DV_TIMINGS 18 .. c:macro:: VIDIOC_QUERY_DV_TIMINGS
19 19
20 ``int ioctl(int fd, VIDIOC_QUERY_DV_TIMINGS, s 20 ``int ioctl(int fd, VIDIOC_QUERY_DV_TIMINGS, struct v4l2_dv_timings *argp)``
21 21
22 .. c:macro:: VIDIOC_SUBDEV_QUERY_DV_TIMINGS 22 .. c:macro:: VIDIOC_SUBDEV_QUERY_DV_TIMINGS
23 23
24 ``int ioctl(int fd, VIDIOC_SUBDEV_QUERY_DV_TIM 24 ``int ioctl(int fd, VIDIOC_SUBDEV_QUERY_DV_TIMINGS, struct v4l2_dv_timings *argp)``
25 25
26 Arguments 26 Arguments
27 ========= 27 =========
28 28
29 ``fd`` 29 ``fd``
30 File descriptor returned by :c:func:`open( 30 File descriptor returned by :c:func:`open()`.
31 31
32 ``argp`` 32 ``argp``
33 Pointer to struct :c:type:`v4l2_dv_timings 33 Pointer to struct :c:type:`v4l2_dv_timings`.
34 34
35 Description 35 Description
36 =========== 36 ===========
37 37
38 The hardware may be able to detect the current 38 The hardware may be able to detect the current DV timings automatically,
39 similar to sensing the video standard. To do s 39 similar to sensing the video standard. To do so, applications call
40 :ref:`VIDIOC_QUERY_DV_TIMINGS` with a pointer 40 :ref:`VIDIOC_QUERY_DV_TIMINGS` with a pointer to a struct
41 :c:type:`v4l2_dv_timings`. Once the hardware d 41 :c:type:`v4l2_dv_timings`. Once the hardware detects
42 the timings, it will fill in the timings struc 42 the timings, it will fill in the timings structure.
43 43
44 .. note:: 44 .. note::
45 45
46 Drivers shall *not* switch timings automati 46 Drivers shall *not* switch timings automatically if new
47 timings are detected. Instead, drivers shou 47 timings are detected. Instead, drivers should send the
48 ``V4L2_EVENT_SOURCE_CHANGE`` event (if they 48 ``V4L2_EVENT_SOURCE_CHANGE`` event (if they support this) and expect
49 that userspace will take action by calling 49 that userspace will take action by calling :ref:`VIDIOC_QUERY_DV_TIMINGS`.
50 The reason is that new timings usually mean 50 The reason is that new timings usually mean different buffer sizes as
51 well, and you cannot change buffer sizes on 51 well, and you cannot change buffer sizes on the fly. In general,
52 applications that receive the Source Change 52 applications that receive the Source Change event will have to call
53 :ref:`VIDIOC_QUERY_DV_TIMINGS`, and if the 53 :ref:`VIDIOC_QUERY_DV_TIMINGS`, and if the detected timings are valid they
54 will have to stop streaming, set the new ti 54 will have to stop streaming, set the new timings, allocate new buffers
55 and start streaming again. 55 and start streaming again.
56 56
57 If the timings could not be detected because t 57 If the timings could not be detected because there was no signal, then
58 ENOLINK is returned. If a signal was detected, 58 ENOLINK is returned. If a signal was detected, but it was unstable and
59 the receiver could not lock to the signal, the 59 the receiver could not lock to the signal, then ``ENOLCK`` is returned. If
60 the receiver could lock to the signal, but the 60 the receiver could lock to the signal, but the format is unsupported
61 (e.g. because the pixelclock is out of range o 61 (e.g. because the pixelclock is out of range of the hardware
62 capabilities), then the driver fills in whatev 62 capabilities), then the driver fills in whatever timings it could find
63 and returns ``ERANGE``. In that case the appli 63 and returns ``ERANGE``. In that case the application can call
64 :ref:`VIDIOC_DV_TIMINGS_CAP` to compare the 64 :ref:`VIDIOC_DV_TIMINGS_CAP` to compare the
65 found timings with the hardware's capabilities 65 found timings with the hardware's capabilities in order to give more
66 precise feedback to the user. 66 precise feedback to the user.
67 67
68 Return Value 68 Return Value
69 ============ 69 ============
70 70
71 On success 0 is returned, on error -1 and the 71 On success 0 is returned, on error -1 and the ``errno`` variable is set
72 appropriately. The generic error codes are des 72 appropriately. The generic error codes are described at the
73 :ref:`Generic Error Codes <gen-errors>` chapte 73 :ref:`Generic Error Codes <gen-errors>` chapter.
74 74
75 ENODATA 75 ENODATA
76 Digital video timings are not supported fo 76 Digital video timings are not supported for this input or output.
77 77
78 ENOLINK 78 ENOLINK
79 No timings could be detected because no si 79 No timings could be detected because no signal was found.
80 80
81 ENOLCK 81 ENOLCK
82 The signal was unstable and the hardware c 82 The signal was unstable and the hardware could not lock on to it.
83 83
84 ERANGE 84 ERANGE
85 Timings were found, but they are out of ra 85 Timings were found, but they are out of range of the hardware
86 capabilities. 86 capabilities.
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