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Diffstat (limited to 'Documentation/linux_tv/media/v4l/vidioc-enum-fmt.rst')
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diff --git a/Documentation/linux_tv/media/v4l/vidioc-enum-fmt.rst b/Documentation/linux_tv/media/v4l/vidioc-enum-fmt.rst new file mode 100644 index 0000000..bcf7eda --- /dev/null +++ b/Documentation/linux_tv/media/v4l/vidioc-enum-fmt.rst @@ -0,0 +1,172 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _vidioc-enum-fmt: + +********************* +ioctl VIDIOC_ENUM_FMT +********************* + +*man VIDIOC_ENUM_FMT(2)* + +Enumerate image formats + + +Synopsis +======== + +.. c: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 ``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. + + +.. ------------------------------------------------------------------------------ +.. This file was automatically converted from DocBook-XML with the dbxml +.. library (https://github.com/return42/sphkerneldoc). The origin XML comes +.. from the linux kernel, refer to: +.. +.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook +.. ------------------------------------------------------------------------------ |