5a26272f9c
This clarifies which side of the calls is responsible for doing what to which parts of the struct. This also explicitly states that repeating values are disallowed. It also expands the terse description of the access algorithm into more prose-like, active voice description, which trades conciseness for ease of comprehension. Added: mbus codes must not repeat Added: no holes in the enumeration Added: enumerations per what? Added: who fills in what in calls Changed: "zero" -> "0" Changed: "given" -> "specified" Still unclear how it works so didn't describe: "which". What is a "try format" vs "active format"? [Sakari Ailus: Rewrap lines, fix build issue] Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm> Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
164 lines
5.4 KiB
ReStructuredText
164 lines
5.4 KiB
ReStructuredText
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. c:namespace:: V4L
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.. _VIDIOC_SUBDEV_ENUM_MBUS_CODE:
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**********************************
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ioctl VIDIOC_SUBDEV_ENUM_MBUS_CODE
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**********************************
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Name
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====
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VIDIOC_SUBDEV_ENUM_MBUS_CODE - Enumerate media bus formats
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Synopsis
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========
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.. c:macro:: VIDIOC_SUBDEV_ENUM_MBUS_CODE
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``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_MBUS_CODE, struct v4l2_subdev_mbus_code_enum * 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_mbus_code_enum`.
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Description
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===========
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This call is used by the application to access the enumeration
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of media bus formats for the selected pad.
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The enumerations are defined by the driver, and indexed using the ``index`` field
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of struct :c:type:`v4l2_subdev_mbus_code_enum`.
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Each enumeration starts with the ``index`` of 0, and
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the lowest invalid index marks the end of enumeration.
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Therefore, to enumerate media bus formats available at a given sub-device pad,
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initialize the ``pad``, and ``which`` fields to desired values,
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and set ``index`` to 0.
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Then call the :ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE` ioctl
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with a pointer to this structure.
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A successful call will return with the ``code`` field filled in
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with a mbus code value.
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Repeat with increasing ``index`` until ``EINVAL`` is received.
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``EINVAL`` means that either ``pad`` is invalid,
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or that there are no more codes available at this pad.
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The driver must not return the same value of ``code`` for different indices
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at the same pad.
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Available media bus formats may depend on the current 'try' formats at
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other pads of the sub-device, as well as on the current active links.
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See :ref:`VIDIOC_SUBDEV_G_FMT` for more
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information about the try formats.
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.. c:type:: v4l2_subdev_mbus_code_enum
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
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.. flat-table:: struct v4l2_subdev_mbus_code_enum
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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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- ``pad``
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- Pad number as reported by the media controller API. Filled in by the
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application.
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* - __u32
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- ``index``
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- Index of the mbus code in the enumeration belonging to the given pad.
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Filled in by the application.
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* - __u32
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- ``code``
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- The media bus format code, as defined in
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:ref:`v4l2-mbus-format`. Filled in by the driver.
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* - __u32
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- ``which``
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- Media bus format codes to be enumerated, from enum
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:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
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* - __u32
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- ``flags``
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- See :ref:`v4l2-subdev-mbus-code-flags`
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* - __u32
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- ``stream``
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- Stream identifier.
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* - __u32
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- ``reserved``\ [6]
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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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.. raw:: latex
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\footnotesize
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.. tabularcolumns:: |p{8.8cm}|p{2.2cm}|p{6.3cm}|
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.. _v4l2-subdev-mbus-code-flags:
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.. flat-table:: Subdev Media Bus Code Enumerate Flags
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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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* - V4L2_SUBDEV_MBUS_CODE_CSC_COLORSPACE
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- 0x00000001
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- The driver allows the application to try to change the default colorspace
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encoding. The application can ask to configure the colorspace of the
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subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
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ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
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See :ref:`v4l2-mbus-format` on how to do this.
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* - V4L2_SUBDEV_MBUS_CODE_CSC_XFER_FUNC
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- 0x00000002
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- The driver allows the application to try to change the default transform function.
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The application can ask to configure the transform function of
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the subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
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ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
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See :ref:`v4l2-mbus-format` on how to do this.
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* - V4L2_SUBDEV_MBUS_CODE_CSC_YCBCR_ENC
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- 0x00000004
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- The driver allows the application to try to change the default Y'CbCr
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encoding. The application can ask to configure the Y'CbCr encoding of the
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subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
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ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
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See :ref:`v4l2-mbus-format` on how to do this.
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* - V4L2_SUBDEV_MBUS_CODE_CSC_HSV_ENC
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- 0x00000004
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- The driver allows the application to try to change the default HSV
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encoding. The application can ask to configure the HSV encoding of the
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subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
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ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
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See :ref:`v4l2-mbus-format` on how to do this.
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* - V4L2_SUBDEV_MBUS_CODE_CSC_QUANTIZATION
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- 0x00000008
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- The driver allows the application to try to change the default
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quantization. The application can ask to configure the quantization of
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the subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
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ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
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See :ref:`v4l2-mbus-format` on how to do this.
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.. raw:: latex
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\normalsize
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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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EINVAL
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The struct
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:c:type:`v4l2_subdev_mbus_code_enum`
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``pad`` references a non-existing pad, or the ``index`` field is out
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of bounds.
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