1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL:
5
6***************************************
7ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
8***************************************
9
10Name
11====
12
13VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL - Enumerate frame intervals
14
15Synopsis
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
22Arguments
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
31Description
32===========
33
34This ioctl lets applications enumerate available frame intervals on a
35given sub-device pad. Frame intervals only makes sense for sub-devices
36that can control the frame period on their own. This includes, for
37instance, image sensors and TV tuners.
38
39For the common use case of image sensors, the frame intervals available
40on the sub-device output pad depend on the frame format and size on the
41same pad. Applications must thus specify the desired format and size
42when enumerating frame intervals.
43
44To 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`
47and call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL` ioctl with a pointer
48to this structure. Drivers fill the rest of the structure or return an
49EINVAL error code if one of the input fields is invalid. All frame
50intervals are enumerable by beginning at index zero and incrementing by
51one until ``EINVAL`` is returned.
52
53Available frame intervals may depend on the current 'try' formats at
54other pads of the sub-device, as well as on the current active links.
55See :ref:`VIDIOC_SUBDEV_G_FMT` for more
56information about the try formats.
57
58Sub-devices that support the frame interval enumeration ioctl should
59implemented it on a single pad only. Its behaviour when supported on
60multiple 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      - ``reserved``\ [8]
96      - Reserved for future extensions. Applications and drivers must set
97	the array to zero.
98
99Return Value
100============
101
102On success 0 is returned, on error -1 and the ``errno`` variable is set
103appropriately. The generic error codes are described at the
104:ref:`Generic Error Codes <gen-errors>` chapter.
105
106EINVAL
107    The struct
108    :c:type:`v4l2_subdev_frame_interval_enum`
109    ``pad`` references a non-existing pad, one of the ``code``,
110    ``width`` or ``height`` fields are invalid for the given pad or the
111    ``index`` field is out of bounds.
112