xref: /linux/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst (revision 54f38fcae536ea202ce7d6a359521492fba30c1f)
1.. Permission is granted to copy, distribute and/or modify this
2.. document under the terms of the GNU Free Documentation License,
3.. Version 1.1 or any later version published by the Free Software
4.. Foundation, with no Invariant Sections, no Front-Cover Texts
5.. and no Back-Cover Texts. A copy of the license is included at
6.. Documentation/userspace-api/media/fdl-appendix.rst.
7..
8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
9
10.. _VIDIOC_SUBDEV_G_CROP:
11
12************************************************
13ioctl VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP
14************************************************
15
16Name
17====
18
19VIDIOC_SUBDEV_G_CROP - VIDIOC_SUBDEV_S_CROP - Get or set the crop rectangle on a subdev pad
20
21
22Synopsis
23========
24
25.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_G_CROP, struct v4l2_subdev_crop *argp )
26    :name: VIDIOC_SUBDEV_G_CROP
27
28.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_S_CROP, const struct v4l2_subdev_crop *argp )
29    :name: VIDIOC_SUBDEV_S_CROP
30
31
32Arguments
33=========
34
35``fd``
36    File descriptor returned by :ref:`open() <func-open>`.
37
38``argp``
39    Pointer to struct :c:type:`v4l2_subdev_crop`.
40
41
42Description
43===========
44
45.. note::
46
47    This is an :ref:`obsolete` interface and may be removed
48    in the future. It is superseded by
49    :ref:`the selection API <VIDIOC_SUBDEV_G_SELECTION>`.
50
51To retrieve the current crop rectangle applications set the ``pad``
52field of a struct :c:type:`v4l2_subdev_crop` to the
53desired pad number as reported by the media API and the ``which`` field
54to ``V4L2_SUBDEV_FORMAT_ACTIVE``. They then call the
55``VIDIOC_SUBDEV_G_CROP`` ioctl with a pointer to this structure. The
56driver fills the members of the ``rect`` field or returns ``EINVAL`` error
57code if the input arguments are invalid, or if cropping is not supported
58on the given pad.
59
60To change the current crop rectangle applications set both the ``pad``
61and ``which`` fields and all members of the ``rect`` field. They then
62call the ``VIDIOC_SUBDEV_S_CROP`` ioctl with a pointer to this
63structure. The driver verifies the requested crop rectangle, adjusts it
64based on the hardware capabilities and configures the device. Upon
65return the struct :c:type:`v4l2_subdev_crop`
66contains the current format as would be returned by a
67``VIDIOC_SUBDEV_G_CROP`` call.
68
69Applications can query the device capabilities by setting the ``which``
70to ``V4L2_SUBDEV_FORMAT_TRY``. When set, 'try' crop rectangles are not
71applied to the device by the driver, but are mangled exactly as active
72crop rectangles and stored in the sub-device file handle. Two
73applications querying the same sub-device would thus not interact with
74each other.
75
76Drivers must not return an error solely because the requested crop
77rectangle doesn't match the device capabilities. They must instead
78modify the rectangle to match what the hardware can provide. The
79modified format should be as close as possible to the original request.
80
81
82.. c:type:: v4l2_subdev_crop
83
84.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
85
86.. flat-table:: struct v4l2_subdev_crop
87    :header-rows:  0
88    :stub-columns: 0
89    :widths:       1 1 2
90
91    * - __u32
92      - ``pad``
93      - Pad number as reported by the media framework.
94    * - __u32
95      - ``which``
96      - Crop rectangle to get or set, from enum
97	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
98    * - struct :c:type:`v4l2_rect`
99      - ``rect``
100      - Crop rectangle boundaries, in pixels.
101    * - __u32
102      - ``reserved``\ [8]
103      - Reserved for future extensions. Applications and drivers must set
104	the array to zero.
105
106
107Return Value
108============
109
110On success 0 is returned, on error -1 and the ``errno`` variable is set
111appropriately. The generic error codes are described at the
112:ref:`Generic Error Codes <gen-errors>` chapter.
113
114EBUSY
115    The crop rectangle can't be changed because the pad is currently
116    busy. This can be caused, for instance, by an active video stream on
117    the pad. The ioctl must not be retried without performing another
118    action to fix the problem first. Only returned by
119    ``VIDIOC_SUBDEV_S_CROP``
120
121EINVAL
122    The struct :c:type:`v4l2_subdev_crop` ``pad``
123    references a non-existing pad, the ``which`` field references a
124    non-existing format, or cropping is not supported on the given
125    subdev pad.
126