diff options
Diffstat (limited to 'Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst')
| -rw-r--r-- | Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst new file mode 100644 index 000000000..f9172a42f --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst @@ -0,0 +1,123 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_SUBDEV_G_SELECTION: + +********************************************************** +ioctl VIDIOC_SUBDEV_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION +********************************************************** + +Name +==== + +VIDIOC_SUBDEV_G_SELECTION - VIDIOC_SUBDEV_S_SELECTION - Get or set selection rectangles on a subdev pad + +Synopsis +======== + +.. c:macro:: VIDIOC_SUBDEV_G_SELECTION + +``int ioctl(int fd, VIDIOC_SUBDEV_G_SELECTION, struct v4l2_subdev_selection *argp)`` + +.. c:macro:: VIDIOC_SUBDEV_S_SELECTION + +``int ioctl(int fd, VIDIOC_SUBDEV_S_SELECTION, struct v4l2_subdev_selection *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_subdev_selection`. + +Description +=========== + +The selections are used to configure various image processing +functionality performed by the subdevs which affect the image size. This +currently includes cropping, scaling and composition. + +The selection API replaces +:ref:`the old subdev crop API <VIDIOC_SUBDEV_G_CROP>`. All the +function of the crop API, and more, are supported by the selections API. + +See :ref:`subdev` for more information on how each selection target +affects the image processing pipeline inside the subdevice. + +If the subdev device node has been registered in read-only mode, calls to +``VIDIOC_SUBDEV_S_SELECTION`` are only valid if the ``which`` field is set to +``V4L2_SUBDEV_FORMAT_TRY``, otherwise an error is returned and the errno +variable is set to ``-EPERM``. + +Types of selection targets +-------------------------- + +There are two types of selection targets: actual and bounds. The actual +targets are the targets which configure the hardware. The BOUNDS target +will return a rectangle that contain all possible actual rectangles. + +Discovering supported features +------------------------------ + +To discover which targets are supported, the user can perform +``VIDIOC_SUBDEV_G_SELECTION`` on them. Any unsupported target will +return ``EINVAL``. + +Selection targets and flags are documented in +:ref:`v4l2-selections-common`. + +.. c:type:: v4l2_subdev_selection + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| + +.. flat-table:: struct v4l2_subdev_selection + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``which`` + - Active or try selection, from enum + :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`. + * - __u32 + - ``pad`` + - Pad number as reported by the media framework. + * - __u32 + - ``target`` + - Target selection rectangle. See :ref:`v4l2-selections-common`. + * - __u32 + - ``flags`` + - Flags. See :ref:`v4l2-selection-flags`. + * - struct :c:type:`v4l2_rect` + - ``r`` + - Selection rectangle, in pixels. + * - __u32 + - ``reserved``\ [8] + - Reserved for future extensions. Applications and drivers must set + the array to zero. + +Return Value +============ + +On success 0 is returned, on error -1 and the ``errno`` variable is set +appropriately. The generic error codes are described at the +:ref:`Generic Error Codes <gen-errors>` chapter. + +EBUSY + The selection rectangle can't be changed because the pad is + currently busy. This can be caused, for instance, by an active video + stream on the pad. The ioctl must not be retried without performing + another action to fix the problem first. Only returned by + ``VIDIOC_SUBDEV_S_SELECTION`` + +EINVAL + The struct :c:type:`v4l2_subdev_selection` + ``pad`` references a non-existing pad, the ``which`` field + references a non-existing format, or the selection target is not + supported on the given subdev pad. + +EPERM + The ``VIDIOC_SUBDEV_S_SELECTION`` ioctl has been called on a read-only + subdevice and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``. |