1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2
3.. _VIDIOC_SUBDEV_G_SELECTION:
4
5**********************************************************
6ioctl VIDIOC_SUBDEV_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION
7**********************************************************
8
9Name
10====
11
12VIDIOC_SUBDEV_G_SELECTION - VIDIOC_SUBDEV_S_SELECTION - Get or set selection rectangles on a subdev pad
13
14
15Synopsis
16========
17
18.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_G_SELECTION, struct v4l2_subdev_selection *argp )
19    :name: VIDIOC_SUBDEV_G_SELECTION
20
21.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_S_SELECTION, struct v4l2_subdev_selection *argp )
22    :name: VIDIOC_SUBDEV_S_SELECTION
23
24
25Arguments
26=========
27
28``fd``
29    File descriptor returned by :ref:`open() <func-open>`.
30
31``argp``
32    Pointer to struct :c:type:`v4l2_subdev_selection`.
33
34
35Description
36===========
37
38The selections are used to configure various image processing
39functionality performed by the subdevs which affect the image size. This
40currently includes cropping, scaling and composition.
41
42The selection API replaces
43:ref:`the old subdev crop API <VIDIOC_SUBDEV_G_CROP>`. All the
44function of the crop API, and more, are supported by the selections API.
45
46See :ref:`subdev` for more information on how each selection target
47affects the image processing pipeline inside the subdevice.
48
49If 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
52variable is set to ``-EPERM``.
53
54Types of selection targets
55--------------------------
56
57There are two types of selection targets: actual and bounds. The actual
58targets are the targets which configure the hardware. The BOUNDS target
59will return a rectangle that contain all possible actual rectangles.
60
61
62Discovering supported features
63------------------------------
64
65To discover which targets are supported, the user can perform
66``VIDIOC_SUBDEV_G_SELECTION`` on them. Any unsupported target will
67return ``EINVAL``.
68
69Selection targets and flags are documented in
70:ref:`v4l2-selections-common`.
71
72
73.. c:type:: v4l2_subdev_selection
74
75.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
76
77.. flat-table:: struct v4l2_subdev_selection
78    :header-rows:  0
79    :stub-columns: 0
80    :widths:       1 1 2
81
82    * - __u32
83      - ``which``
84      - Active or try selection, from enum
85	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
86    * - __u32
87      - ``pad``
88      - Pad number as reported by the media framework.
89    * - __u32
90      - ``target``
91      - Target selection rectangle. See :ref:`v4l2-selections-common`.
92    * - __u32
93      - ``flags``
94      - Flags. See :ref:`v4l2-selection-flags`.
95    * - struct :c:type:`v4l2_rect`
96      - ``r``
97      - Selection rectangle, in pixels.
98    * - __u32
99      - ``reserved``\ [8]
100      - Reserved for future extensions. Applications and drivers must set
101	the array to zero.
102
103
104Return Value
105============
106
107On success 0 is returned, on error -1 and the ``errno`` variable is set
108appropriately. The generic error codes are described at the
109:ref:`Generic Error Codes <gen-errors>` chapter.
110
111EBUSY
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
118EINVAL
119    The struct :c:type:`v4l2_subdev_selection`
120    ``pad`` references a non-existing pad, the ``which`` field
121    references a non-existing format, or the selection target is not
122    supported on the given subdev pad.
123
124EPERM
125    The ``VIDIOC_SUBDEV_S_SELECTION`` ioctl has been called on a read-only
126    subdevice and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``.
127