1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL:
5
6 ***************************************
7 ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
8 ***************************************
9
10 Name
11 ====
12
13 VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL - Enumerate frame intervals
14
15 Synopsis
16 ========
17
18 .. c:macro:: VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
19
20 ``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL, struct v4l2_subdev_frame_interval_enum * argp)``
21
22 Arguments
23 =========
24
25 ``fd``
26 File descriptor returned by :c:func:`open()`.
27
28 ``argp``
29 Pointer to struct :c:type:`v4l2_subdev_frame_interval_enum`.
30
31 Description
32 ===========
33
34 This ioctl lets applications enumerate available frame intervals on a
35 given sub-device pad. Frame intervals only makes sense for sub-devices
36 that can control the frame period on their own. This includes, for
37 instance, image sensors and TV tuners.
38
39 For the common use case of image sensors, the frame intervals available
40 on the sub-device output pad depend on the frame format and size on the
41 same pad. Applications must thus specify the desired format and size
42 when enumerating frame intervals.
43
44 To enumerate frame intervals applications initialize the ``index``,
45 ``pad``, ``which``, ``code``, ``width`` and ``height`` fields of struct
46 :c:type:`v4l2_subdev_frame_interval_enum`
47 and call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL` ioctl with a pointer
48 to this structure. Drivers fill the rest of the structure or return an
49 EINVAL error code if one of the input fields is invalid. All frame
50 intervals are enumerable by beginning at index zero and incrementing by
51 one until ``EINVAL`` is returned.
52
53 Available frame intervals may depend on the current 'try' formats at
54 other pads of the sub-device, as well as on the current active links.
55 See :ref:`VIDIOC_SUBDEV_G_FMT` for more
56 information about the try formats.
57
58 Sub-devices that support the frame interval enumeration ioctl should
59 implemented it on a single pad only. Its behaviour when supported on
60 multiple pads of the same sub-device is not defined.
61
62 .. c:type:: v4l2_subdev_frame_interval_enum
63
64 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
65
66 .. flat-table:: struct v4l2_subdev_frame_interval_enum
67 :header-rows: 0
68 :stub-columns: 0
69 :widths: 1 1 2
70
71 * - __u32
72 - ``index``
73 - Number of the format in the enumeration, set by the application.
74 * - __u32
75 - ``pad``
76 - Pad number as reported by the media controller API.
77 * - __u32
78 - ``code``
79 - The media bus format code, as defined in
80 :ref:`v4l2-mbus-format`.
81 * - __u32
82 - ``width``
83 - Frame width, in pixels.
84 * - __u32
85 - ``height``
86 - Frame height, in pixels.
87 * - struct :c:type:`v4l2_fract`
88 - ``interval``
89 - Period, in seconds, between consecutive video frames.
90 * - __u32
91 - ``which``
92 - Frame intervals to be enumerated, from enum
93 :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
94 * - __u32
95 - ``stream``
96 - Stream identifier.
97 * - __u32
98 - ``reserved``\ [7]
99 - Reserved for future extensions. Applications and drivers must set
100 the array to zero.
101
102 Return Value
103 ============
104
105 On success 0 is returned, on error -1 and the ``errno`` variable is set
106 appropriately. The generic error codes are described at the
107 :ref:`Generic Error Codes <gen-errors>` chapter.
108
109 EINVAL
110 The struct :c:type:`v4l2_subdev_frame_interval_enum` ``pad`` references a
111 non-existing pad, the ``which`` field has an unsupported value, one of the
112 ``code``, ``width`` or ``height`` fields are invalid for the given pad, or
113 the ``index`` field is out of bounds.
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