vidioc-subdev-g-crop.rst (4304B)
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 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 It is superseded by 42 :ref:`the selection API 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.. 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 - ``reserved``\ [8] 100 - Reserved for future extensions. Applications and drivers must set 101 the array to zero. 102 103Return Value 104============ 105 106On success 0 is returned, on error -1 and the ``errno`` variable is set 107appropriately. The generic error codes are described at the 108:ref:`Generic Error Codes <gen-errors>` chapter. 109 110EBUSY 111 The crop rectangle can't be changed because the pad is currently 112 busy. This can be caused, for instance, by an active video stream on 113 the pad. The ioctl must not be retried without performing another 114 action to fix the problem first. Only returned by 115 ``VIDIOC_SUBDEV_S_CROP`` 116 117EINVAL 118 The struct :c:type:`v4l2_subdev_crop` ``pad`` 119 references a non-existing pad, the ``which`` field references a 120 non-existing format, or cropping is not supported on the given 121 subdev pad. 122 123EPERM 124 The ``VIDIOC_SUBDEV_S_CROP`` ioctl has been called on a read-only subdevice 125 and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``.