VIDIOC_SUBDEV_ENUM_MBUS_CODE ioctl

목적, 호출 형식과 인자

`VIDIOC_SUBDEV_ENUM_MBUS_CODE`는 선택한 서브디바이스 pad에서 사용할 수 있는 media-bus 형식 코드를 열거합니다. `argp`는 `struct v4l2_subdev_mbus_code_enum`을 가리킵니다.

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: V4L

.. _VIDIOC_SUBDEV_ENUM_MBUS_CODE:

**********************************
ioctl VIDIOC_SUBDEV_ENUM_MBUS_CODE
**********************************

Name
====

VIDIOC_SUBDEV_ENUM_MBUS_CODE - Enumerate media bus formats

Synopsis
========

.. c:macro:: VIDIOC_SUBDEV_ENUM_MBUS_CODE

``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_MBUS_CODE, struct v4l2_subdev_mbus_code_enum * argp)``

Arguments
=========

``fd``
    File descriptor returned by :c:func:`open()`.

``argp``
    Pointer to struct :c:type:`v4l2_subdev_mbus_code_enum`.

열거 규칙과 파이프라인 의존성

드라이버가 pad별 열거 목록을 정의하며 `index = 0`에서 시작합니다. 응용 프로그램은 `pad`와 `which`를 설정한 뒤 인덱스를 1씩 늘려 호출합니다.

성공하면 드라이버가 `code`에 media-bus 형식 코드를 채웁니다. `EINVAL`은 pad가 잘못되었거나 해당 pad에서 더 이상 반환할 코드가 없음을 나타냅니다.

같은 pad의 서로 다른 인덱스에서 드라이버가 동일한 `code`를 중복 반환해서는 안 됩니다. 따라서 성공한 각 인덱스는 고유한 형식 항목입니다.

사용 가능한 형식은 다른 pad의 try format과 현재 활성 링크에 의존할 수 있습니다. `VIDIOC_SUBDEV_G_FMT`의 try format 규칙을 함께 적용해야 합니다.

Description
===========

This call is used by the application to access the enumeration
of media bus formats for the selected pad.

The enumerations are defined by the driver, and indexed using the ``index`` field
of struct :c:type:`v4l2_subdev_mbus_code_enum`.
Each enumeration starts with the ``index`` of 0, and
the lowest invalid index marks the end of enumeration.

Therefore, to enumerate media bus formats available at a given sub-device pad,
initialize the ``pad``, and ``which`` fields to desired values,
and set ``index`` to 0.
Then call the :ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE` ioctl
with a pointer to this structure.

A successful call will return with the ``code`` field filled in
with a mbus code value.
Repeat with increasing ``index`` until ``EINVAL`` is received.
``EINVAL`` means that either ``pad`` is invalid,
or that there are no more codes available at this pad.

The driver must not return the same value of ``code`` for different indices
at the same pad.

Available media bus formats may depend on the current 'try' formats at
other pads of the sub-device, as well as on the current active links.
See :ref:`VIDIOC_SUBDEV_G_FMT` for more
information about the try formats.

struct v4l2_subdev_mbus_code_enum

.. c:type:: v4l2_subdev_mbus_code_enum

.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|

.. flat-table:: struct v4l2_subdev_mbus_code_enum
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2

    * - __u32
      - ``pad``
      - Pad number as reported by the media controller API. Filled in by the
        application.
    * - __u32
      - ``index``
      - Index of the mbus code in the enumeration belonging to the given pad.
        Filled in by the application.
    * - __u32
      - ``code``
      - The media bus format code, as defined in
	:ref:`v4l2-mbus-format`. Filled in by the driver.
    * - __u32
      - ``which``
      - Media bus format codes to be enumerated, from enum
	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
    * - __u32
      - ``flags``
      - See :ref:`v4l2-subdev-mbus-code-flags`
    * - __u32
      - ``stream``
      - Stream identifier.
    * - __u32
      - ``reserved``\ [6]
      - Reserved for future extensions. Applications and drivers must set
	the array to zero.

색 공간 변환 관련 flags

다음 flags는 `VIDIOC_SUBDEV_S_FMT`를 호출할 때 `V4L2_MBUS_FRAMEFMT_SET_CSC`를 설정해 기본 색 표현의 특정 요소를 변경하도록 시도할 수 있음을 알립니다. 실제 구성 절차는 `v4l2-mbus-format` 규칙을 따릅니다.

Y'CbCr와 HSV encoding flag는 원문 정의상 모두 `0x00000004`를 사용합니다. 현재 code가 나타내는 색 표현에 따라 해당 의미를 해석해야 합니다.

.. raw:: latex

   \footnotesize

.. tabularcolumns:: |p{8.8cm}|p{2.2cm}|p{6.3cm}|

.. _v4l2-subdev-mbus-code-flags:

.. flat-table:: Subdev Media Bus Code Enumerate Flags
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2

    * - V4L2_SUBDEV_MBUS_CODE_CSC_COLORSPACE
      - 0x00000001
      - The driver allows the application to try to change the default colorspace
	encoding. The application can ask to configure the colorspace of the
	subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
	ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
	See :ref:`v4l2-mbus-format` on how to do this.
    * - V4L2_SUBDEV_MBUS_CODE_CSC_XFER_FUNC
      - 0x00000002
      - The driver allows the application to try to change the default transform function.
	The application can ask to configure the transform function of
	the subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
	ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
	See :ref:`v4l2-mbus-format` on how to do this.
    * - V4L2_SUBDEV_MBUS_CODE_CSC_YCBCR_ENC
      - 0x00000004
      - The driver allows the application to try to change the default Y'CbCr
	encoding. The application can ask to configure the Y'CbCr encoding of the
	subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
	ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
	See :ref:`v4l2-mbus-format` on how to do this.
    * - V4L2_SUBDEV_MBUS_CODE_CSC_HSV_ENC
      - 0x00000004
      - The driver allows the application to try to change the default HSV
	encoding. The application can ask to configure the HSV encoding of the
	subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
	ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
	See :ref:`v4l2-mbus-format` on how to do this.
    * - V4L2_SUBDEV_MBUS_CODE_CSC_QUANTIZATION
      - 0x00000008
      - The driver allows the application to try to change the default
	quantization. The application can ask to configure the quantization of
	the subdevice when calling the :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>`
	ioctl with :ref:`V4L2_MBUS_FRAMEFMT_SET_CSC <mbus-framefmt-set-csc>` set.
	See :ref:`v4l2-mbus-format` on how to do this.

.. raw:: latex

   \normalsize

반환값과 EINVAL

성공하면 0, 오류이면 -1을 반환하고 `errno`를 설정합니다.

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.

EINVAL
    The struct :c:type:`v4l2_subdev_mbus_code_enum` ``pad`` references a
    non-existing pad, the ``which`` field has an unsupported value, or the
    ``index`` field is out of bounds.