1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2
3.. _VIDIOC_SUBDEV_G_CROP:
4
5************************************************
6ioctl VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP
7************************************************
8
9Name
10====
11
12VIDIOC_SUBDEV_G_CROP - VIDIOC_SUBDEV_S_CROP - Get or set the crop rectangle on a subdev pad
13
14
15Synopsis
16========
17
18.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_G_CROP, struct v4l2_subdev_crop *argp )
19    :name: VIDIOC_SUBDEV_G_CROP
20
21.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_S_CROP, const struct v4l2_subdev_crop *argp )
22    :name: VIDIOC_SUBDEV_S_CROP
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_crop`.
33
34
35Description
36===========
37
38.. note::
39
40    This is an :ref:`obsolete` interface and may be removed
41    in the future. It is superseded by
42    :ref:`the selection API <VIDIOC_SUBDEV_G_SELECTION>`.
43
44To retrieve the current crop rectangle applications set the ``pad``
45field of a struct :c:type:`v4l2_subdev_crop` to the
46desired pad number as reported by the media API and the ``which`` field
47to ``V4L2_SUBDEV_FORMAT_ACTIVE``. They then call the
48``VIDIOC_SUBDEV_G_CROP`` ioctl with a pointer to this structure. The
49driver fills the members of the ``rect`` field or returns ``EINVAL`` error
50code if the input arguments are invalid, or if cropping is not supported
51on the given pad.
52
53To change the current crop rectangle applications set both the ``pad``
54and ``which`` fields and all members of the ``rect`` field. They then
55call the ``VIDIOC_SUBDEV_S_CROP`` ioctl with a pointer to this
56structure. The driver verifies the requested crop rectangle, adjusts it
57based on the hardware capabilities and configures the device. Upon
58return the struct :c:type:`v4l2_subdev_crop`
59contains the current format as would be returned by a
60``VIDIOC_SUBDEV_G_CROP`` call.
61
62Applications can query the device capabilities by setting the ``which``
63to ``V4L2_SUBDEV_FORMAT_TRY``. When set, 'try' crop rectangles are not
64applied to the device by the driver, but are mangled exactly as active
65crop rectangles and stored in the sub-device file handle. Two
66applications querying the same sub-device would thus not interact with
67each other.
68
69If the subdev device node has been registered in read-only mode, calls to
70``VIDIOC_SUBDEV_S_CROP`` are only valid if the ``which`` field is set to
71``V4L2_SUBDEV_FORMAT_TRY``, otherwise an error is returned and the errno
72variable is set to ``-EPERM``.
73
74Drivers must not return an error solely because the requested crop
75rectangle doesn't match the device capabilities. They must instead
76modify the rectangle to match what the hardware can provide. The
77modified format should be as close as possible to the original request.
78
79
80.. c:type:: v4l2_subdev_crop
81
82.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
83
84.. flat-table:: struct v4l2_subdev_crop
85    :header-rows:  0
86    :stub-columns: 0
87    :widths:       1 1 2
88
89    * - __u32
90      - ``pad``
91      - Pad number as reported by the media framework.
92    * - __u32
93      - ``which``
94      - Crop rectangle to get or set, from enum
95	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
96    * - struct :c:type:`v4l2_rect`
97      - ``rect``
98      - Crop rectangle boundaries, in pixels.
99    * - __u32
100      - ``reserved``\ [8]
101      - Reserved for future extensions. Applications and drivers must set
102	the array to zero.
103
104
105Return Value
106============
107
108On success 0 is returned, on error -1 and the ``errno`` variable is set
109appropriately. The generic error codes are described at the
110:ref:`Generic Error Codes <gen-errors>` chapter.
111
112EBUSY
113    The crop rectangle can't be changed because the pad is currently
114    busy. This can be caused, for instance, by an active video stream on
115    the pad. The ioctl must not be retried without performing another
116    action to fix the problem first. Only returned by
117    ``VIDIOC_SUBDEV_S_CROP``
118
119EINVAL
120    The struct :c:type:`v4l2_subdev_crop` ``pad``
121    references a non-existing pad, the ``which`` field references a
122    non-existing format, or cropping is not supported on the given
123    subdev pad.
124
125EPERM
126    The ``VIDIOC_SUBDEV_S_CROP`` ioctl has been called on a read-only subdevice
127    and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``.
128