Documentation/linux_tv/media/v4l/vidioc-subdev-g-crop.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _VIDIOC_SUBDEV_G_CROP:
   4
   5 ************************************************
   6 ioctl VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP
   7 ************************************************
   8
   9 NAME
  10 ====
  11
  12 VIDIOC_SUBDEV_G_CROP - VIDIOC_SUBDEV_S_CROP - Get or set the crop rectangle on a subdev pad
  13
  14 SYNOPSIS
  15 ========
  16
  17 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_subdev_crop *argp )
  18
  19 .. cpp:function:: int ioctl( int fd, int request, const struct v4l2_subdev_crop *argp )
  20
  21
  22 ARGUMENTS
  23 =========
  24
  25 ``fd``
  26     File descriptor returned by :ref:`open() <func-open>`.
  27
  28 ``request``
  29     VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP
  30
  31 ``argp``
  32
  33
  34 DESCRIPTION
  35 ===========
  36
  37     **Note**
  38
  39     This is an :ref:`obsolete` interface and may be removed
  40     in the future. It is superseded by
  41     :ref:`the selection API <VIDIOC_SUBDEV_G_SELECTION>`.
  42
  43 To retrieve the current crop rectangle applications set the ``pad``
  44 field of a struct :ref:`v4l2_subdev_crop <v4l2-subdev-crop>` to the
  45 desired pad number as reported by the media API and the ``which`` field
  46 to ``V4L2_SUBDEV_FORMAT_ACTIVE``. They then call the
  47 ``VIDIOC_SUBDEV_G_CROP`` ioctl with a pointer to this structure. The
  48 driver fills the members of the ``rect`` field or returns ``EINVAL`` error
  49 code if the input arguments are invalid, or if cropping is not supported
  50 on the given pad.
  51
  52 To change the current crop rectangle applications set both the ``pad``
  53 and ``which`` fields and all members of the ``rect`` field. They then
  54 call the ``VIDIOC_SUBDEV_S_CROP`` ioctl with a pointer to this
  55 structure. The driver verifies the requested crop rectangle, adjusts it
  56 based on the hardware capabilities and configures the device. Upon
  57 return the struct :ref:`v4l2_subdev_crop <v4l2-subdev-crop>`
  58 contains the current format as would be returned by a
  59 ``VIDIOC_SUBDEV_G_CROP`` call.
  60
  61 Applications can query the device capabilities by setting the ``which``
  62 to ``V4L2_SUBDEV_FORMAT_TRY``. When set, 'try' crop rectangles are not
  63 applied to the device by the driver, but are mangled exactly as active
  64 crop rectangles and stored in the sub-device file handle. Two
  65 applications querying the same sub-device would thus not interact with
  66 each other.
  67
  68 Drivers must not return an error solely because the requested crop
  69 rectangle doesn't match the device capabilities. They must instead
  70 modify the rectangle to match what the hardware can provide. The
  71 modified format should be as close as possible to the original request.
  72
  73
  74 .. _v4l2-subdev-crop:
  75
  76 .. flat-table:: struct v4l2_subdev_crop
  77     :header-rows:  0
  78     :stub-columns: 0
  79     :widths:       1 1 2
  80
  81
  82     -  .. row 1
  83
  84        -  __u32
  85
  86        -  ``pad``
  87
  88        -  Pad number as reported by the media framework.
  89
  90     -  .. row 2
  91
  92        -  __u32
  93
  94        -  ``which``
  95
  96        -  Crop rectangle to get or set, from enum
  97           :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
  98
  99     -  .. row 3
 100
 101        -  struct :ref:`v4l2_rect <v4l2-rect>`
 102
 103        -  ``rect``
 104
 105        -  Crop rectangle boundaries, in pixels.
 106
 107     -  .. row 4
 108
 109        -  __u32
 110
 111        -  ``reserved``\ [8]
 112
 113        -  Reserved for future extensions. Applications and drivers must set
 114           the array to zero.
 115
 116
 117 RETURN VALUE
 118 ============
 119
 120 On success 0 is returned, on error -1 and the ``errno`` variable is set
 121 appropriately. The generic error codes are described at the
 122 :ref:`Generic Error Codes <gen-errors>` chapter.
 123
 124 EBUSY
 125     The crop rectangle can't be changed because the pad is currently
 126     busy. This can be caused, for instance, by an active video stream on
 127     the pad. The ioctl must not be retried without performing another
 128     action to fix the problem first. Only returned by
 129     ``VIDIOC_SUBDEV_S_CROP``
 130
 131 EINVAL
 132     The struct :ref:`v4l2_subdev_crop <v4l2-subdev-crop>` ``pad``
 133     references a non-existing pad, the ``which`` field references a
 134     non-existing format, or cropping is not supported on the given
 135     subdev pad.