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authorMauro Carvalho Chehab <mchehab@s-opensource.com>2016-07-08 17:40:06 +0300
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2016-07-08 17:59:40 +0300
commit60c2820d0f6d3497975b6488e2599f8f611d8b95 (patch)
treeb3b03707c6438ea9b99cc57e847ebf517f968ab1 /Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
parenta97369b5e21ea9b8b5fef7c0f4f48bbe60c07ca3 (diff)
downloadlinux-60c2820d0f6d3497975b6488e2599f8f611d8b95.tar.xz
doc_rst: rename the media Sphinx suff to Documentation/media
The name of the subsystem is "media", and not "linux_tv". Also, as we plan to add other stuff there in the future, let's rename also the media uAPI book to media_uapi, to make it clearer. No functional changes. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _VIDIOC_ENUM_FMT:
+
+*********************
+ioctl VIDIOC_ENUM_FMT
+*********************
+
+Name
+====
+
+VIDIOC_ENUM_FMT - Enumerate image formats
+
+
+Synopsis
+========
+
+.. cpp:function:: int ioctl( int fd, int request, struct v4l2_fmtdesc *argp )
+
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``request``
+ VIDIOC_ENUM_FMT
+
+``argp``
+
+
+Description
+===========
+
+To enumerate image formats applications initialize the ``type`` and
+``index`` field of struct :ref:`v4l2_fmtdesc <v4l2-fmtdesc>` and call
+the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers
+fill the rest of the structure or return an ``EINVAL`` error code. All
+formats are enumerable by beginning at index zero and incrementing by
+one until ``EINVAL`` is returned.
+
+Note that after switching input or output the list of enumerated image
+formats may be different.
+
+
+.. _v4l2-fmtdesc:
+
+.. flat-table:: struct v4l2_fmtdesc
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 2
+
+
+ - .. row 1
+
+ - __u32
+
+ - ``index``
+
+ - Number of the format in the enumeration, set by the application.
+ This is in no way related to the ``pixelformat`` field.
+
+ - .. row 2
+
+ - __u32
+
+ - ``type``
+
+ - Type of the data stream, set by the application. Only these types
+ are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
+ ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``,
+ ``V4L2_BUF_TYPE_VIDEO_OUTPUT``,
+ ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and
+ ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :ref:`v4l2-buf-type`.
+
+ - .. row 3
+
+ - __u32
+
+ - ``flags``
+
+ - See :ref:`fmtdesc-flags`
+
+ - .. row 4
+
+ - __u8
+
+ - ``description``\ [32]
+
+ - Description of the format, a NUL-terminated ASCII string. This
+ information is intended for the user, for example: "YUV 4:2:2".
+
+ - .. row 5
+
+ - __u32
+
+ - ``pixelformat``
+
+ - The image format identifier. This is a four character code as
+ computed by the v4l2_fourcc() macro:
+
+ - .. row 6
+
+ - :cspan:`2`
+
+
+ .. _v4l2-fourcc:
+ .. code-block:: c
+
+ #define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))
+
+ Several image formats are already defined by this specification in
+ :ref:`pixfmt`. Note these codes are not the same as those used
+ in the Windows world.
+
+ - .. row 7
+
+ - __u32
+
+ - ``reserved``\ [4]
+
+ - Reserved for future extensions. Drivers must set the array to
+ zero.
+
+
+
+.. _fmtdesc-flags:
+
+.. flat-table:: Image Format Description Flags
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 4
+
+
+ - .. row 1
+
+ - ``V4L2_FMT_FLAG_COMPRESSED``
+
+ - 0x0001
+
+ - This is a compressed format.
+
+ - .. row 2
+
+ - ``V4L2_FMT_FLAG_EMULATED``
+
+ - 0x0002
+
+ - This format is not native to the device but emulated through
+ software (usually libv4l2), where possible try to use a native
+ format instead for better performance.
+
+
+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 :ref:`v4l2_fmtdesc <v4l2-fmtdesc>` ``type`` is not
+ supported or the ``index`` is out of bounds.