1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _VIDIOC_SUBDEV_G_SELECTION:
5
6 **********************************************************
7 ioctl VIDIOC_SUBDEV_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION
8 **********************************************************
9
10 Name
11 ====
12
13 VIDIOC_SUBDEV_G_SELECTION - VIDIOC_SUBDEV_S_SELECTION - Get or set selection rectangles on a subdev pad
14
15 Synopsis
16 ========
17
18 .. c:macro:: VIDIOC_SUBDEV_G_SELECTION
19
20 ``int ioctl(int fd, VIDIOC_SUBDEV_G_SELECTION, struct v4l2_subdev_selection *argp)``
21
22 .. c:macro:: VIDIOC_SUBDEV_S_SELECTION
23
24 ``int ioctl(int fd, VIDIOC_SUBDEV_S_SELECTION, struct v4l2_subdev_selection *argp)``
25
26 Arguments
27 =========
28
29 ``fd``
30 File descriptor returned by :c:func:`open()`.
31
32 ``argp``
33 Pointer to struct :c:type:`v4l2_subdev_selection`.
34
35 Description
36 ===========
37
38 The selections are used to configure various image processing
39 functionality performed by the subdevs which affect the image size. This
40 currently includes cropping, scaling and composition.
41
42 The selection API replaces
43 :ref:`the old subdev crop API <VIDIOC_SUBDEV_G_CROP>`. All the
44 function of the crop API, and more, are supported by the selections API.
45
46 See :ref:`subdev` for more information on how each selection target
47 affects the image processing pipeline inside the subdevice.
48
49 If the subdev device node has been registered in read-only mode, calls to
50 ``VIDIOC_SUBDEV_S_SELECTION`` are only valid if the ``which`` field is set to
51 ``V4L2_SUBDEV_FORMAT_TRY``, otherwise an error is returned and the errno
52 variable is set to ``-EPERM``.
53
54 Types of selection targets
55 --------------------------
56
57 There are two types of selection targets: actual and bounds. The actual
58 targets are the targets which configure the hardware. The BOUNDS target
59 will return a rectangle that contain all possible actual rectangles.
60
61 Discovering supported features
62 ------------------------------
63
64 To discover which targets are supported, the user can perform
65 ``VIDIOC_SUBDEV_G_SELECTION`` on them. Any unsupported target will
66 return ``EINVAL``.
67
68 Selection targets and flags are documented in
69 :ref:`v4l2-selections-common`.
70
71 .. c:type:: v4l2_subdev_selection
72
73 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
74
75 .. flat-table:: struct v4l2_subdev_selection
76 :header-rows: 0
77 :stub-columns: 0
78 :widths: 1 1 2
79
80 * - __u32
81 - ``which``
82 - Active or try selection, from enum
83 :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
84 * - __u32
85 - ``pad``
86 - Pad number as reported by the media framework.
87 * - __u32
88 - ``target``
89 - Target selection rectangle. See :ref:`v4l2-selections-common`.
90 * - __u32
91 - ``flags``
92 - Flags. See :ref:`v4l2-selection-flags`.
93 * - struct :c:type:`v4l2_rect`
94 - ``r``
95 - Selection rectangle, in pixels.
96 * - __u32
97 - ``stream``
98 - Stream identifier.
99 * - __u32
100 - ``reserved``\ [7]
101 - Reserved for future extensions. Applications and drivers must set
102 the array to zero.
103
104 Return Value
105 ============
106
107 On success 0 is returned, on error -1 and the ``errno`` variable is set
108 appropriately. The generic error codes are described at the
109 :ref:`Generic Error Codes <gen-errors>` chapter.
110
111 EBUSY
112 The selection rectangle can't be changed because the pad is
113 currently busy. This can be caused, for instance, by an active video
114 stream on the pad. The ioctl must not be retried without performing
115 another action to fix the problem first. Only returned by
116 ``VIDIOC_SUBDEV_S_SELECTION``
117
118 EINVAL
119 The struct :c:type:`v4l2_subdev_selection` ``pad`` references a
120 non-existing pad, the ``which`` field has an unsupported value, or the
121 selection target is not supported on the given subdev pad.
122
123 EPERM
124 The ``VIDIOC_SUBDEV_S_SELECTION`` ioctl has been called on a read-only
125 subdevice and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``.
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