media: docs: move uAPI book to userspace-api/media
Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee3862 ("docs: Create a user-space API guide").
As the media subsystem was one of the first subsystems to use
Sphinx, until this patch, we were keeping things on a separate
place.
Let's just use the new location, as having all uAPI altogether
will likely make things easier for developers.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-enc-index.rst b/Documentation/userspace-api/media/v4l/vidioc-g-enc-index.rst
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+.. Permission is granted to copy, distribute and/or modify this
+.. document under the terms of the GNU Free Documentation License,
+.. Version 1.1 or any later version published by the Free Software
+.. Foundation, with no Invariant Sections, no Front-Cover Texts
+.. and no Back-Cover Texts. A copy of the license is included at
+.. Documentation/userspace-api/media/fdl-appendix.rst.
+..
+.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _VIDIOC_G_ENC_INDEX:
+
+************************
+ioctl VIDIOC_G_ENC_INDEX
+************************
+
+Name
+====
+
+VIDIOC_G_ENC_INDEX - Get meta data about a compressed video stream
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_G_ENC_INDEX, struct v4l2_enc_idx *argp )
+ :name: VIDIOC_G_ENC_INDEX
+
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_enc_idx`.
+
+
+Description
+===========
+
+The :ref:`VIDIOC_G_ENC_INDEX <VIDIOC_G_ENC_INDEX>` ioctl provides meta data about a compressed
+video stream the same or another application currently reads from the
+driver, which is useful for random access into the stream without
+decoding it.
+
+To read the data applications must call :ref:`VIDIOC_G_ENC_INDEX <VIDIOC_G_ENC_INDEX>` with a
+pointer to a struct :c:type:`v4l2_enc_idx`. On success
+the driver fills the ``entry`` array, stores the number of elements
+written in the ``entries`` field, and initializes the ``entries_cap``
+field.
+
+Each element of the ``entry`` array contains meta data about one
+picture. A :ref:`VIDIOC_G_ENC_INDEX <VIDIOC_G_ENC_INDEX>` call reads up to
+``V4L2_ENC_IDX_ENTRIES`` entries from a driver buffer, which can hold up
+to ``entries_cap`` entries. This number can be lower or higher than
+``V4L2_ENC_IDX_ENTRIES``, but not zero. When the application fails to
+read the meta data in time the oldest entries will be lost. When the
+buffer is empty or no capturing/encoding is in progress, ``entries``
+will be zero.
+
+Currently this ioctl is only defined for MPEG-2 program streams and
+video elementary streams.
+
+
+.. tabularcolumns:: |p{3.8cm}|p{5.6cm}|p{8.1cm}|
+
+.. c:type:: v4l2_enc_idx
+
+.. flat-table:: struct v4l2_enc_idx
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 3 8
+
+ * - __u32
+ - ``entries``
+ - The number of entries the driver stored in the ``entry`` array.
+ * - __u32
+ - ``entries_cap``
+ - The number of entries the driver can buffer. Must be greater than
+ zero.
+ * - __u32
+ - ``reserved``\ [4]
+ - Reserved for future extensions. Drivers must set the
+ array to zero.
+ * - struct :c:type:`v4l2_enc_idx_entry`
+ - ``entry``\ [``V4L2_ENC_IDX_ENTRIES``]
+ - Meta data about a compressed video stream. Each element of the
+ array corresponds to one picture, sorted in ascending order by
+ their ``offset``.
+
+
+
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
+.. c:type:: v4l2_enc_idx_entry
+
+.. flat-table:: struct v4l2_enc_idx_entry
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 2
+
+ * - __u64
+ - ``offset``
+ - The offset in bytes from the beginning of the compressed video
+ stream to the beginning of this picture, that is a *PES packet
+ header* as defined in :ref:`mpeg2part1` or a *picture header* as
+ defined in :ref:`mpeg2part2`. When the encoder is stopped, the
+ driver resets the offset to zero.
+ * - __u64
+ - ``pts``
+ - The 33 bit *Presentation Time Stamp* of this picture as defined in
+ :ref:`mpeg2part1`.
+ * - __u32
+ - ``length``
+ - The length of this picture in bytes.
+ * - __u32
+ - ``flags``
+ - Flags containing the coding type of this picture, see
+ :ref:`enc-idx-flags`.
+ * - __u32
+ - ``reserved``\ [2]
+ - Reserved for future extensions. Drivers must set the array to
+ zero.
+
+
+.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
+
+.. _enc-idx-flags:
+
+.. flat-table:: Index Entry Flags
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 4
+
+ * - ``V4L2_ENC_IDX_FRAME_I``
+ - 0x00
+ - This is an Intra-coded picture.
+ * - ``V4L2_ENC_IDX_FRAME_P``
+ - 0x01
+ - This is a Predictive-coded picture.
+ * - ``V4L2_ENC_IDX_FRAME_B``
+ - 0x02
+ - This is a Bidirectionally predictive-coded picture.
+ * - ``V4L2_ENC_IDX_FRAME_MASK``
+ - 0x0F
+ - *AND* the flags field with this mask to obtain the picture coding
+ type.
+
+
+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.