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