1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_SUBDEV_G_SELECTION:
5
6**********************************************************
7ioctl VIDIOC_SUBDEV_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION
8**********************************************************
9
10Name
11====
12
13VIDIOC_SUBDEV_G_SELECTION - VIDIOC_SUBDEV_S_SELECTION - Get or set selection rectangles on a subdev pad
14
15Synopsis
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
26Arguments
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
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
61Discovering supported features
62------------------------------
63
64To discover which targets are supported, the user can perform
65``VIDIOC_SUBDEV_G_SELECTION`` on them. Any unsupported target will
66return ``EINVAL``.
67
68Selection 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      - ``reserved``\ [8]
98      - Reserved for future extensions. Applications and drivers must set
99	the array to zero.
100
101Return Value
102============
103
104On success 0 is returned, on error -1 and the ``errno`` variable is set
105appropriately. The generic error codes are described at the
106:ref:`Generic Error Codes <gen-errors>` chapter.
107
108EBUSY
109    The selection rectangle can't be changed because the pad is
110    currently busy. This can be caused, for instance, by an active video
111    stream on the pad. The ioctl must not be retried without performing
112    another action to fix the problem first. Only returned by
113    ``VIDIOC_SUBDEV_S_SELECTION``
114
115EINVAL
116    The struct :c:type:`v4l2_subdev_selection`
117    ``pad`` references a non-existing pad, the ``which`` field
118    references a non-existing format, or the selection target is not
119    supported on the given subdev pad.
120
121EPERM
122    The ``VIDIOC_SUBDEV_S_SELECTION`` ioctl has been called on a read-only
123    subdevice and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``.
124