vidioc-subdev-g-crop.rst

  1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
  2.. c:namespace:: V4L
  3
  4.. _VIDIOC_SUBDEV_G_CROP:
  5
  6************************************************
  7ioctl VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP
  8************************************************
  9
 10Name
 11====
 12
 13VIDIOC_SUBDEV_G_CROP - VIDIOC_SUBDEV_S_CROP - Get or set the crop rectangle on a subdev pad
 14
 15Synopsis
 16========
 17
 18.. c:macro:: VIDIOC_SUBDEV_G_CROP
 19
 20``int ioctl(int fd, VIDIOC_SUBDEV_G_CROP, struct v4l2_subdev_crop *argp)``
 21
 22.. c:macro:: VIDIOC_SUBDEV_S_CROP
 23
 24``int ioctl(int fd, VIDIOC_SUBDEV_S_CROP, const struct v4l2_subdev_crop *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_crop`.
 34
 35Description
 36===========
 37
 38.. note::
 39
 40    This is an :ref:`obsolete` interface and may be removed in the future. It is
 41    superseded by :ref:`the selection API <VIDIOC_SUBDEV_G_SELECTION>`. No new
 42    extensions to the :c:type:`v4l2_subdev_crop` structure will be accepted.
 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.. c:type:: v4l2_subdev_crop
 80
 81.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
 82
 83.. flat-table:: struct v4l2_subdev_crop
 84    :header-rows:  0
 85    :stub-columns: 0
 86    :widths:       1 1 2
 87
 88    * - __u32
 89      - ``pad``
 90      - Pad number as reported by the media framework.
 91    * - __u32
 92      - ``which``
 93      - Crop rectangle to get or set, from enum
 94	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
 95    * - struct :c:type:`v4l2_rect`
 96      - ``rect``
 97      - Crop rectangle boundaries, in pixels.
 98    * - __u32
 99      - ``stream``
100      - Stream identifier.
101    * - __u32
102      - ``reserved``\ [7]
103      - Reserved for future extensions. Applications and drivers must set
104	the array to zero.
105
106Return Value
107============
108
109On success 0 is returned, on error -1 and the ``errno`` variable is set
110appropriately. The generic error codes are described at the
111:ref:`Generic Error Codes <gen-errors>` chapter.
112
113EBUSY
114    The crop rectangle can't be changed because the pad is currently
115    busy. This can be caused, for instance, by an active video stream on
116    the pad. The ioctl must not be retried without performing another
117    action to fix the problem first. Only returned by
118    ``VIDIOC_SUBDEV_S_CROP``
119
120EINVAL
121    The struct :c:type:`v4l2_subdev_crop` ``pad`` references a non-existing pad,
122    the ``which`` field has an unsupported value, or cropping is not supported
123    on the given 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``.