Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1276 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/v4l/hist-v4l2.rst b/Documentation/userspace-api/media/v4l/hist-v4l2.rst
new file mode 100644
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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _hist-v4l2:
+
+***********************
+Changes of the V4L2 API
+***********************
+
+Soon after the V4L API was added to the kernel it was criticised as too
+inflexible. In August 1998 Bill Dirks proposed a number of improvements
+and began to work on documentation, example drivers and applications.
+With the help of other volunteers this eventually became the V4L2 API,
+not just an extension but a replacement for the V4L API. However it took
+another four years and two stable kernel releases until the new API was
+finally accepted for inclusion into the kernel in its present form.
+
+Early Versions
+==============
+
+1998-08-20: First version.
+
+1998-08-27: The :c:func:`select()` function was introduced.
+
+1998-09-10: New video standard interface.
+
+1998-09-18: The ``VIDIOC_NONCAP`` ioctl was replaced by the otherwise
+meaningless ``O_TRUNC`` :c:func:`open()` flag, and the
+aliases ``O_NONCAP`` and ``O_NOIO`` were defined. Applications can set
+this flag if they intend to access controls only, as opposed to capture
+applications which need exclusive access. The ``VIDEO_STD_XXX``
+identifiers are now ordinals instead of flags, and the
+``video_std_construct()`` helper function takes id and
+transmission arguments.
+
+1998-09-28: Revamped video standard. Made video controls individually
+enumerable.
+
+1998-10-02: The ``id`` field was removed from
+struct ``video_standard`` and the color subcarrier fields were
+renamed. The :ref:`VIDIOC_QUERYSTD` ioctl was
+renamed to :ref:`VIDIOC_ENUMSTD`,
+:ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` to
+:ref:`VIDIOC_ENUMINPUT`. A first draft of the
+Codec API was released.
+
+1998-11-08: Many minor changes. Most symbols have been renamed. Some
+material changes to struct v4l2_capability.
+
+1998-11-12: The read/write directon of some ioctls was misdefined.
+
+1998-11-14: ``V4L2_PIX_FMT_RGB24`` changed to ``V4L2_PIX_FMT_BGR24``,
+and ``V4L2_PIX_FMT_RGB32`` changed to ``V4L2_PIX_FMT_BGR32``. Audio
+controls are now accessible with the
+:ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` and
+:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls under names starting
+with ``V4L2_CID_AUDIO``. The ``V4L2_MAJOR`` define was removed from
+``videodev.h`` since it was only used once in the ``videodev`` kernel
+module. The ``YUV422`` and ``YUV411`` planar image formats were added.
+
+1998-11-28: A few ioctl symbols changed. Interfaces for codecs and video
+output devices were added.
+
+1999-01-14: A raw VBI capture interface was added.
+
+1999-01-19: The ``VIDIOC_NEXTBUF`` ioctl was removed.
+
+V4L2 Version 0.16 1999-01-31
+============================
+
+1999-01-27: There is now one QBUF ioctl, VIDIOC_QWBUF and VIDIOC_QRBUF
+are gone. VIDIOC_QBUF takes a v4l2_buffer as a parameter. Added
+digital zoom (cropping) controls.
+
+V4L2 Version 0.18 1999-03-16
+============================
+
+Added a v4l to V4L2 ioctl compatibility layer to videodev.c. Driver
+writers, this changes how you implement your ioctl handler. See the
+Driver Writer's Guide. Added some more control id codes.
+
+V4L2 Version 0.19 1999-06-05
+============================
+
+1999-03-18: Fill in the category and catname fields of v4l2_queryctrl
+objects before passing them to the driver. Required a minor change to
+the VIDIOC_QUERYCTRL handlers in the sample drivers.
+
+1999-03-31: Better compatibility for v4l memory capture ioctls. Requires
+changes to drivers to fully support new compatibility features, see
+Driver Writer's Guide and v4l2cap.c. Added new control IDs:
+V4L2_CID_HFLIP, _VFLIP. Changed V4L2_PIX_FMT_YUV422P to _YUV422P,
+and _YUV411P to _YUV411P.
+
+1999-04-04: Added a few more control IDs.
+
+1999-04-07: Added the button control type.
+
+1999-05-02: Fixed a typo in videodev.h, and added the
+V4L2_CTRL_FLAG_GRAYED (later V4L2_CTRL_FLAG_GRABBED) flag.
+
+1999-05-20: Definition of VIDIOC_G_CTRL was wrong causing a
+malfunction of this ioctl.
+
+1999-06-05: Changed the value of V4L2_CID_WHITENESS.
+
+V4L2 Version 0.20 (1999-09-10)
+==============================
+
+Version 0.20 introduced a number of changes which were *not backward
+compatible* with 0.19 and earlier versions. Purpose of these changes was
+to simplify the API, while making it more extensible and following
+common Linux driver API conventions.
+
+1. Some typos in ``V4L2_FMT_FLAG`` symbols were fixed. struct v4l2_clip
+   was changed for compatibility with v4l. (1999-08-30)
+
+2. ``V4L2_TUNER_SUB_LANG1`` was added. (1999-09-05)
+
+3. All ioctl() commands that used an integer argument now take a pointer
+   to an integer. Where it makes sense, ioctls will return the actual
+   new value in the integer pointed to by the argument, a common
+   convention in the V4L2 API. The affected ioctls are: VIDIOC_PREVIEW,
+   VIDIOC_STREAMON, VIDIOC_STREAMOFF, VIDIOC_S_FREQ,
+   VIDIOC_S_INPUT, VIDIOC_S_OUTPUT, VIDIOC_S_EFFECT. For example
+
+   .. code-block:: c
+
+       err = ioctl (fd, VIDIOC_XXX, V4L2_XXX);
+
+   becomes
+
+   .. code-block:: c
+
+       int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a);
+
+4. All the different get- and set-format commands were swept into one
+   :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
+   :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl taking a union and a
+   type field selecting the union member as parameter. Purpose is to
+   simplify the API by eliminating several ioctls and to allow new and
+   driver private data streams without adding new ioctls.
+
+   This change obsoletes the following ioctls: ``VIDIOC_S_INFMT``,
+   ``VIDIOC_G_INFMT``, ``VIDIOC_S_OUTFMT``, ``VIDIOC_G_OUTFMT``,
+   ``VIDIOC_S_VBIFMT`` and ``VIDIOC_G_VBIFMT``. The image format
+   struct v4l2_format was renamed to struct v4l2_pix_format, while
+   struct v4l2_format is now the envelopping structure
+   for all format negotiations.
+
+5. Similar to the changes above, the ``VIDIOC_G_PARM`` and
+   ``VIDIOC_S_PARM`` ioctls were merged with ``VIDIOC_G_OUTPARM`` and
+   ``VIDIOC_S_OUTPARM``. A ``type`` field in the new struct v4l2_streamparm
+   selects the respective union member.
+
+   This change obsoletes the ``VIDIOC_G_OUTPARM`` and
+   ``VIDIOC_S_OUTPARM`` ioctls.
+
+6. Control enumeration was simplified, and two new control flags were
+   introduced and one dropped. The ``catname`` field was replaced by a
+   ``group`` field.
+
+   Drivers can now flag unsupported and temporarily unavailable controls
+   with ``V4L2_CTRL_FLAG_DISABLED`` and ``V4L2_CTRL_FLAG_GRABBED``
+   respectively. The ``group`` name indicates a possibly narrower
+   classification than the ``category``. In other words, there may be
+   multiple groups within a category. Controls within a group would
+   typically be drawn within a group box. Controls in different
+   categories might have a greater separation, or may even appear in
+   separate windows.
+
+7. The struct v4l2_buffer ``timestamp`` was
+   changed to a 64 bit integer, containing the sampling or output time
+   of the frame in nanoseconds. Additionally timestamps will be in
+   absolute system time, not starting from zero at the beginning of a
+   stream. The data type name for timestamps is stamp_t, defined as a
+   signed 64-bit integer. Output devices should not send a buffer out
+   until the time in the timestamp field has arrived. I would like to
+   follow SGI's lead, and adopt a multimedia timestamping system like
+   their UST (Unadjusted System Time). See
+   http://web.archive.org/web/\*/http://reality.sgi.com
+   /cpirazzi_engr/lg/time/intro.html. UST uses timestamps that are
+   64-bit signed integers (not struct timeval's) and given in nanosecond
+   units. The UST clock starts at zero when the system is booted and
+   runs continuously and uniformly. It takes a little over 292 years for
+   UST to overflow. There is no way to set the UST clock. The regular
+   Linux time-of-day clock can be changed periodically, which would
+   cause errors if it were being used for timestamping a multimedia
+   stream. A real UST style clock will require some support in the
+   kernel that is not there yet. But in anticipation, I will change the
+   timestamp field to a 64-bit integer, and I will change the
+   v4l2_masterclock_gettime() function (used only by drivers) to
+   return a 64-bit integer.
+
+8. A ``sequence`` field was added to struct v4l2_buffer. The ``sequence``
+   field counts captured frames, it is ignored by output devices. When a
+   capture driver drops a frame, the sequence number of that frame is skipped.
+
+V4L2 Version 0.20 incremental changes
+=====================================
+
+1999-12-23: In struct v4l2_vbi_format the
+``reserved1`` field became ``offset``. Previously drivers were required
+to clear the ``reserved1`` field.
+
+2000-01-13: The ``V4L2_FMT_FLAG_NOT_INTERLACED`` flag was added.
+
+2000-07-31: The ``linux/poll.h`` header is now included by
+``videodev.h`` for compatibility with the original ``videodev.h`` file.
+
+2000-11-20: ``V4L2_TYPE_VBI_OUTPUT`` and ``V4L2_PIX_FMT_Y41P`` were
+added.
+
+2000-11-25: ``V4L2_TYPE_VBI_INPUT`` was added.
+
+2000-12-04: A couple typos in symbol names were fixed.
+
+2001-01-18: To avoid namespace conflicts the ``fourcc`` macro defined in
+the ``videodev.h`` header file was renamed to ``v4l2_fourcc``.
+
+2001-01-25: A possible driver-level compatibility problem between the
+``videodev.h`` file in Linux 2.4.0 and the ``videodev.h`` file included
+in the ``videodevX`` patch was fixed. Users of an earlier version of
+``videodevX`` on Linux 2.4.0 should recompile their V4L and V4L2
+drivers.
+
+2001-01-26: A possible kernel-level incompatibility between the
+``videodev.h`` file in the ``videodevX`` patch and the ``videodev.h``
+file in Linux 2.2.x with devfs patches applied was fixed.
+
+2001-03-02: Certain V4L ioctls which pass data in both direction
+although they are defined with read-only parameter, did not work
+correctly through the backward compatibility layer. [Solution?]
+
+2001-04-13: Big endian 16-bit RGB formats were added.
+
+2001-09-17: New YUV formats and the
+:ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` and
+:ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctls were added.
+(The old ``VIDIOC_G_FREQ`` and ``VIDIOC_S_FREQ`` ioctls did not take
+multiple tuners into account.)
+
+2000-09-18: ``V4L2_BUF_TYPE_VBI`` was added. This may *break
+compatibility* as the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
+:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls may fail now if the
+struct ``v4l2_fmt`` ``type`` field does not contain
+``V4L2_BUF_TYPE_VBI``. In the documentation of the struct v4l2_vbi_format`,
+the ``offset`` field the ambiguous phrase "rising edge" was changed to
+"leading edge".
+
+V4L2 Version 0.20 2000-11-23
+============================
+
+A number of changes were made to the raw VBI interface.
+
+1. Figures clarifying the line numbering scheme were added to the V4L2
+   API specification. The ``start``\ [0] and ``start``\ [1] fields no
+   longer count line numbers beginning at zero. Rationale: a) The
+   previous definition was unclear. b) The ``start``\ [] values are
+   ordinal numbers. c) There is no point in inventing a new line
+   numbering scheme. We now use line number as defined by ITU-R, period.
+   Compatibility: Add one to the start values. Applications depending on
+   the previous semantics may not function correctly.
+
+2. The restriction "count[0] > 0 and count[1] > 0" has been relaxed to
+   "(count[0] + count[1]) > 0". Rationale: Drivers may allocate
+   resources at scan line granularity and some data services are
+   transmitted only on the first field. The comment that both ``count``
+   values will usually be equal is misleading and pointless and has been
+   removed. This change *breaks compatibility* with earlier versions:
+   Drivers may return ``EINVAL``, applications may not function correctly.
+
+3. Drivers are again permitted to return negative (unknown) start values
+   as proposed earlier. Why this feature was dropped is unclear. This
+   change may *break compatibility* with applications depending on the
+   start values being positive. The use of ``EBUSY`` and ``EINVAL``
+   error codes with the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl was
+   clarified. The ``EBUSY`` error code was finally documented, and the
+   ``reserved2`` field which was previously mentioned only in the
+   ``videodev.h`` header file.
+
+4. New buffer types ``V4L2_TYPE_VBI_INPUT`` and ``V4L2_TYPE_VBI_OUTPUT``
+   were added. The former is an alias for the old ``V4L2_TYPE_VBI``, the
+   latter was missing in the ``videodev.h`` file.
+
+V4L2 Version 0.20 2002-07-25
+============================
+
+Added sliced VBI interface proposal.
+
+V4L2 in Linux 2.5.46, 2002-10
+=============================
+
+Around October-November 2002, prior to an announced feature freeze of
+Linux 2.5, the API was revised, drawing from experience with V4L2 0.20.
+This unnamed version was finally merged into Linux 2.5.46.
+
+1.  As specified in :ref:`related`, drivers must make related device
+    functions available under all minor device numbers.
+
+2.  The :c:func:`open()` function requires access mode
+    ``O_RDWR`` regardless of the device type. All V4L2 drivers
+    exchanging data with applications must support the ``O_NONBLOCK``
+    flag. The ``O_NOIO`` flag, a V4L2 symbol which aliased the
+    meaningless ``O_TRUNC`` to indicate accesses without data exchange
+    (panel applications) was dropped. Drivers must stay in "panel mode"
+    until the application attempts to initiate a data exchange, see
+    :ref:`open`.
+
+3.  The struct v4l2_capability changed
+    dramatically. Note that also the size of the structure changed,
+    which is encoded in the ioctl request code, thus older V4L2 devices
+    will respond with an ``EINVAL`` error code to the new
+    :ref:`VIDIOC_QUERYCAP` ioctl.
+
+    There are new fields to identify the driver, a new RDS device
+    function ``V4L2_CAP_RDS_CAPTURE``, the ``V4L2_CAP_AUDIO`` flag
+    indicates if the device has any audio connectors, another I/O
+    capability ``V4L2_CAP_ASYNCIO`` can be flagged. In response to these
+    changes the ``type`` field became a bit set and was merged into the
+    ``flags`` field. ``V4L2_FLAG_TUNER`` was renamed to
+    ``V4L2_CAP_TUNER``, ``V4L2_CAP_VIDEO_OVERLAY`` replaced
+    ``V4L2_FLAG_PREVIEW`` and ``V4L2_CAP_VBI_CAPTURE`` and
+    ``V4L2_CAP_VBI_OUTPUT`` replaced ``V4L2_FLAG_DATA_SERVICE``.
+    ``V4L2_FLAG_READ`` and ``V4L2_FLAG_WRITE`` were merged into
+    ``V4L2_CAP_READWRITE``.
+
+    The redundant fields ``inputs``, ``outputs`` and ``audios`` were
+    removed. These properties can be determined as described in
+    :ref:`video` and :ref:`audio`.
+
+    The somewhat volatile and therefore barely useful fields
+    ``maxwidth``, ``maxheight``, ``minwidth``, ``minheight``,
+    ``maxframerate`` were removed. This information is available as
+    described in :ref:`format` and :ref:`standard`.
+
+    ``V4L2_FLAG_SELECT`` was removed. We believe the select() function
+    is important enough to require support of it in all V4L2 drivers
+    exchanging data with applications. The redundant
+    ``V4L2_FLAG_MONOCHROME`` flag was removed, this information is
+    available as described in :ref:`format`.
+
+4.  In struct v4l2_input the ``assoc_audio``
+    field and the ``capability`` field and its only flag
+    ``V4L2_INPUT_CAP_AUDIO`` was replaced by the new ``audioset`` field.
+    Instead of linking one video input to one audio input this field
+    reports all audio inputs this video input combines with.
+
+    New fields are ``tuner`` (reversing the former link from tuners to
+    video inputs), ``std`` and ``status``.
+
+    Accordingly struct v4l2_output lost its
+    ``capability`` and ``assoc_audio`` fields. ``audioset``,
+    ``modulator`` and ``std`` where added instead.
+
+5.  The struct v4l2_audio field ``audio`` was
+    renamed to ``index``, for consistency with other structures. A new
+    capability flag ``V4L2_AUDCAP_STEREO`` was added to indicated if the
+    audio input in question supports stereo sound.
+    ``V4L2_AUDCAP_EFFECTS`` and the corresponding ``V4L2_AUDMODE`` flags
+    where removed. This can be easily implemented using controls.
+    (However the same applies to AVL which is still there.)
+
+    Again for consistency the struct v4l2_audioout field ``audio`` was renamed
+    to ``index``.
+
+6.  The struct v4l2_tuner ``input`` field was
+    replaced by an ``index`` field, permitting devices with multiple
+    tuners. The link between video inputs and tuners is now reversed,
+    inputs point to their tuner. The ``std`` substructure became a
+    simple set (more about this below) and moved into struct v4l2_input.
+    A ``type`` field was added.
+
+    Accordingly in struct v4l2_modulator the
+    ``output`` was replaced by an ``index`` field.
+
+    In struct v4l2_frequency the ``port``
+    field was replaced by a ``tuner`` field containing the respective
+    tuner or modulator index number. A tuner ``type`` field was added
+    and the ``reserved`` field became larger for future extensions
+    (satellite tuners in particular).
+
+7.  The idea of completely transparent video standards was dropped.
+    Experience showed that applications must be able to work with video
+    standards beyond presenting the user a menu. Instead of enumerating
+    supported standards with an ioctl applications can now refer to
+    standards by :ref:`v4l2_std_id <v4l2-std-id>` and symbols
+    defined in the ``videodev2.h`` header file. For details see
+    :ref:`standard`. The :ref:`VIDIOC_G_STD <VIDIOC_G_STD>` and
+    :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` now take a pointer to this
+    type as argument. :ref:`VIDIOC_QUERYSTD` was
+    added to autodetect the received standard, if the hardware has this
+    capability. In struct v4l2_standard an
+    ``index`` field was added for
+    :ref:`VIDIOC_ENUMSTD`. A
+    :ref:`v4l2_std_id <v4l2-std-id>` field named ``id`` was added as
+    machine readable identifier, also replacing the ``transmission``
+    field. The misleading ``framerate`` field was renamed to
+    ``frameperiod``. The now obsolete ``colorstandard`` information,
+    originally needed to distguish between variations of standards, were
+    removed.
+
+    Struct ``v4l2_enumstd`` ceased to be.
+    :ref:`VIDIOC_ENUMSTD` now takes a pointer to a
+    struct v4l2_standard directly. The
+    information which standards are supported by a particular video
+    input or output moved into struct v4l2_input
+    and struct v4l2_output fields named ``std``,
+    respectively.
+
+8.  The struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` fields
+    ``category`` and ``group`` did not catch on and/or were not
+    implemented as expected and therefore removed.
+
+9.  The :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl was added to
+    negotiate data formats as with
+    :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`, but without the overhead of
+    programming the hardware and regardless of I/O in progress.
+
+    In struct v4l2_format the ``fmt`` union was
+    extended to contain struct v4l2_window. All
+    image format negotiations are now possible with ``VIDIOC_G_FMT``,
+    ``VIDIOC_S_FMT`` and ``VIDIOC_TRY_FMT``; ioctl. The ``VIDIOC_G_WIN``
+    and ``VIDIOC_S_WIN`` ioctls to prepare for a video overlay were
+    removed. The ``type`` field changed to type enum v4l2_buf_type and
+    the buffer type names changed as follows.
+
+
+    .. flat-table::
+	:header-rows:  1
+	:stub-columns: 0
+
+	* - Old defines
+	  - enum v4l2_buf_type
+	* - ``V4L2_BUF_TYPE_CAPTURE``
+	  - ``V4L2_BUF_TYPE_VIDEO_CAPTURE``
+	* - ``V4L2_BUF_TYPE_CODECIN``
+	  - Omitted for now
+	* - ``V4L2_BUF_TYPE_CODECOUT``
+	  - Omitted for now
+	* - ``V4L2_BUF_TYPE_EFFECTSIN``
+	  - Omitted for now
+	* - ``V4L2_BUF_TYPE_EFFECTSIN2``
+	  - Omitted for now
+	* - ``V4L2_BUF_TYPE_EFFECTSOUT``
+	  - Omitted for now
+	* - ``V4L2_BUF_TYPE_VIDEOOUT``
+	  - ``V4L2_BUF_TYPE_VIDEO_OUTPUT``
+	* - ``-``
+	  - ``V4L2_BUF_TYPE_VIDEO_OVERLAY``
+	* - ``-``
+	  - ``V4L2_BUF_TYPE_VBI_CAPTURE``
+	* - ``-``
+	  - ``V4L2_BUF_TYPE_VBI_OUTPUT``
+	* - ``-``
+	  - ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE``
+	* - ``-``
+	  - ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT``
+	* - ``V4L2_BUF_TYPE_PRIVATE_BASE``
+	  - ``V4L2_BUF_TYPE_PRIVATE`` (but this is deprecated)
+
+10. In struct v4l2_fmtdesc a enum v4l2_buf_type field named ``type`` was
+    added as in struct v4l2_format. The ``VIDIOC_ENUM_FBUFFMT`` ioctl is no
+    longer needed and was removed. These calls can be replaced by
+    :ref:`VIDIOC_ENUM_FMT` with type ``V4L2_BUF_TYPE_VIDEO_OVERLAY``.
+
+11. In struct v4l2_pix_format the ``depth``
+    field was removed, assuming applications which recognize the format
+    by its four-character-code already know the color depth, and others
+    do not care about it. The same rationale lead to the removal of the
+    ``V4L2_FMT_FLAG_COMPRESSED`` flag. The
+    ``V4L2_FMT_FLAG_SWCONVECOMPRESSED`` flag was removed because drivers
+    are not supposed to convert images in kernel space. A user library
+    of conversion functions should be provided instead. The
+    ``V4L2_FMT_FLAG_BYTESPERLINE`` flag was redundant. Applications can
+    set the ``bytesperline`` field to zero to get a reasonable default.
+    Since the remaining flags were replaced as well, the ``flags`` field
+    itself was removed.
+
+    The interlace flags were replaced by a enum v4l2_field value in a
+    newly added ``field`` field.
+
+    .. flat-table::
+	:header-rows:  1
+	:stub-columns: 0
+
+	* - Old flag
+	  - enum v4l2_field
+	* - ``V4L2_FMT_FLAG_NOT_INTERLACED``
+	  - ?
+	* - ``V4L2_FMT_FLAG_INTERLACED`` = ``V4L2_FMT_FLAG_COMBINED``
+	  - ``V4L2_FIELD_INTERLACED``
+	* - ``V4L2_FMT_FLAG_TOPFIELD`` = ``V4L2_FMT_FLAG_ODDFIELD``
+	  - ``V4L2_FIELD_TOP``
+	* - ``V4L2_FMT_FLAG_BOTFIELD`` = ``V4L2_FMT_FLAG_EVENFIELD``
+	  - ``V4L2_FIELD_BOTTOM``
+	* - ``-``
+	  - ``V4L2_FIELD_SEQ_TB``
+	* - ``-``
+	  - ``V4L2_FIELD_SEQ_BT``
+	* - ``-``
+	  - ``V4L2_FIELD_ALTERNATE``
+
+    The color space flags were replaced by a enum v4l2_colorspace value in
+    a newly added ``colorspace`` field, where one of
+    ``V4L2_COLORSPACE_SMPTE170M``, ``V4L2_COLORSPACE_BT878``,
+    ``V4L2_COLORSPACE_470_SYSTEM_M`` or
+    ``V4L2_COLORSPACE_470_SYSTEM_BG`` replaces ``V4L2_FMT_CS_601YUV``.
+
+12. In struct v4l2_requestbuffers the
+    ``type`` field was properly defined as enum v4l2_buf_type. Buffer types
+    changed as mentioned above. A new ``memory`` field of type
+    enum v4l2_memory was added to distinguish between
+    I/O methods using buffers allocated by the driver or the
+    application. See :ref:`io` for details.
+
+13. In struct v4l2_buffer the ``type`` field was
+    properly defined as enum v4l2_buf_type.
+    Buffer types changed as mentioned above. A ``field`` field of type
+    enum v4l2_field was added to indicate if a
+    buffer contains a top or bottom field. The old field flags were
+    removed. Since no unadjusted system time clock was added to the
+    kernel as planned, the ``timestamp`` field changed back from type
+    stamp_t, an unsigned 64 bit integer expressing the sample time in
+    nanoseconds, to struct timeval. With the addition
+    of a second memory mapping method the ``offset`` field moved into
+    union ``m``, and a new ``memory`` field of type enum v4l2_memory
+    was added to distinguish between
+    I/O methods. See :ref:`io` for details.
+
+    The ``V4L2_BUF_REQ_CONTIG`` flag was used by the V4L compatibility
+    layer, after changes to this code it was no longer needed. The
+    ``V4L2_BUF_ATTR_DEVICEMEM`` flag would indicate if the buffer was
+    indeed allocated in device memory rather than DMA-able system
+    memory. It was barely useful and so was removed.
+
+14. In struct v4l2_framebuffer the
+    ``base[3]`` array anticipating double- and triple-buffering in
+    off-screen video memory, however without defining a synchronization
+    mechanism, was replaced by a single pointer. The
+    ``V4L2_FBUF_CAP_SCALEUP`` and ``V4L2_FBUF_CAP_SCALEDOWN`` flags were
+    removed. Applications can determine this capability more accurately
+    using the new cropping and scaling interface. The
+    ``V4L2_FBUF_CAP_CLIPPING`` flag was replaced by
+    ``V4L2_FBUF_CAP_LIST_CLIPPING`` and
+    ``V4L2_FBUF_CAP_BITMAP_CLIPPING``.
+
+15. In struct v4l2_clip the ``x``, ``y``,
+    ``width`` and ``height`` field moved into a ``c`` substructure of
+    type struct v4l2_rect. The ``x`` and ``y``
+    fields were renamed to ``left`` and ``top``, i. e. offsets to a
+    context dependent origin.
+
+16. In struct v4l2_window the ``x``, ``y``,
+    ``width`` and ``height`` field moved into a ``w`` substructure as
+    above. A ``field`` field of type enum v4l2_field was added to
+    distinguish between field and frame (interlaced) overlay.
+
+17. The digital zoom interface, including struct ``v4l2_zoomcap``,
+    struct ``v4l2_zoom``, ``V4L2_ZOOM_NONCAP`` and
+    ``V4L2_ZOOM_WHILESTREAMING`` was replaced by a new cropping and
+    scaling interface. The previously unused
+    struct v4l2_cropcap and struct v4l2_crop
+    where redefined for this purpose. See :ref:`crop` for details.
+
+18. In struct v4l2_vbi_format the
+    ``SAMPLE_FORMAT`` field now contains a four-character-code as used
+    to identify video image formats and ``V4L2_PIX_FMT_GREY`` replaces
+    the ``V4L2_VBI_SF_UBYTE`` define. The ``reserved`` field was
+    extended.
+
+19. In struct v4l2_captureparm the type of
+    the ``timeperframe`` field changed from unsigned long to
+    struct v4l2_fract. This allows the accurate
+    expression of multiples of the NTSC-M frame rate 30000 / 1001. A new
+    field ``readbuffers`` was added to control the driver behaviour in
+    read I/O mode.
+
+    Similar changes were made to struct v4l2_outputparm.
+
+20. The struct ``v4l2_performance`` and
+    ``VIDIOC_G_PERF`` ioctl were dropped. Except when using the
+    :ref:`read/write I/O method <rw>`, which is limited anyway, this
+    information is already available to applications.
+
+21. The example transformation from RGB to YCbCr color space in the old
+    V4L2 documentation was inaccurate, this has been corrected in
+    :ref:`pixfmt`.
+
+V4L2 2003-06-19
+===============
+
+1. A new capability flag ``V4L2_CAP_RADIO`` was added for radio devices.
+   Prior to this change radio devices would identify solely by having
+   exactly one tuner whose type field reads ``V4L2_TUNER_RADIO``.
+
+2. An optional driver access priority mechanism was added, see
+   :ref:`app-pri` for details.
+
+3. The audio input and output interface was found to be incomplete.
+
+   Previously the :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl would
+   enumerate the available audio inputs. An ioctl to determine the
+   current audio input, if more than one combines with the current video
+   input, did not exist. So ``VIDIOC_G_AUDIO`` was renamed to
+   ``VIDIOC_G_AUDIO_OLD``, this ioctl was removed on Kernel 2.6.39. The
+   :ref:`VIDIOC_ENUMAUDIO` ioctl was added to
+   enumerate audio inputs, while
+   :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` now reports the current
+   audio input.
+
+   The same changes were made to
+   :ref:`VIDIOC_G_AUDOUT <VIDIOC_G_AUDOUT>` and
+   :ref:`VIDIOC_ENUMAUDOUT <VIDIOC_ENUMAUDOUT>`.
+
+   Until further the "videodev" module will automatically translate
+   between the old and new ioctls, but drivers and applications must be
+   updated to successfully compile again.
+
+4. The :ref:`VIDIOC_OVERLAY` ioctl was incorrectly
+   defined with write-read parameter. It was changed to write-only,
+   while the write-read version was renamed to ``VIDIOC_OVERLAY_OLD``.
+   The old ioctl was removed on Kernel 2.6.39. Until further the
+   "videodev" kernel module will automatically translate to the new
+   version, so drivers must be recompiled, but not applications.
+
+5. :ref:`overlay` incorrectly stated that clipping rectangles define
+   regions where the video can be seen. Correct is that clipping
+   rectangles define regions where *no* video shall be displayed and so
+   the graphics surface can be seen.
+
+6. The :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` and
+   :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls were defined with
+   write-only parameter, inconsistent with other ioctls modifying their
+   argument. They were changed to write-read, while a ``_OLD`` suffix
+   was added to the write-only versions. The old ioctls were removed on
+   Kernel 2.6.39. Drivers and applications assuming a constant parameter
+   need an update.
+
+V4L2 2003-11-05
+===============
+
+1. In :ref:`pixfmt-rgb` the following pixel formats were incorrectly
+   transferred from Bill Dirks' V4L2 specification. Descriptions below
+   refer to bytes in memory, in ascending address order.
+
+
+   .. flat-table::
+       :header-rows:  1
+       :stub-columns: 0
+
+       * - Symbol
+	 - In this document prior to revision 0.5
+	 - Corrected
+       * - ``V4L2_PIX_FMT_RGB24``
+	 - B, G, R
+	 - R, G, B
+       * - ``V4L2_PIX_FMT_BGR24``
+	 - R, G, B
+	 - B, G, R
+       * - ``V4L2_PIX_FMT_RGB32``
+	 - B, G, R, X
+	 - R, G, B, X
+       * - ``V4L2_PIX_FMT_BGR32``
+	 - R, G, B, X
+	 - B, G, R, X
+
+   The ``V4L2_PIX_FMT_BGR24`` example was always correct.
+
+   In :ref:`v4l-image-properties` the mapping of the V4L
+   ``VIDEO_PALETTE_RGB24`` and ``VIDEO_PALETTE_RGB32`` formats to V4L2
+   pixel formats was accordingly corrected.
+
+2. Unrelated to the fixes above, drivers may still interpret some V4L2
+   RGB pixel formats differently. These issues have yet to be addressed,
+   for details see :ref:`pixfmt-rgb`.
+
+V4L2 in Linux 2.6.6, 2004-05-09
+===============================
+
+1. The :ref:`VIDIOC_CROPCAP` ioctl was incorrectly
+   defined with read-only parameter. It is now defined as write-read
+   ioctl, while the read-only version was renamed to
+   ``VIDIOC_CROPCAP_OLD``. The old ioctl was removed on Kernel 2.6.39.
+
+V4L2 in Linux 2.6.8
+===================
+
+1. A new field ``input`` (former ``reserved[0]``) was added to the
+   struct v4l2_buffer. Purpose of this
+   field is to alternate between video inputs (e. g. cameras) in step
+   with the video capturing process. This function must be enabled with
+   the new ``V4L2_BUF_FLAG_INPUT`` flag. The ``flags`` field is no
+   longer read-only.
+
+V4L2 spec erratum 2004-08-01
+============================
+
+1. The return value of the :ref:`func-open` function was incorrectly
+   documented.
+
+2. Audio output ioctls end in -AUDOUT, not -AUDIOOUT.
+
+3. In the Current Audio Input example the ``VIDIOC_G_AUDIO`` ioctl took
+   the wrong argument.
+
+4. The documentation of the :ref:`VIDIOC_QBUF` and
+   :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctls did not mention the
+   struct v4l2_buffer ``memory`` field. It was
+   also missing from examples. Also on the ``VIDIOC_DQBUF`` page the ``EIO``
+   error code was not documented.
+
+V4L2 in Linux 2.6.14
+====================
+
+1. A new sliced VBI interface was added. It is documented in
+   :ref:`sliced` and replaces the interface first proposed in V4L2
+   specification 0.8.
+
+V4L2 in Linux 2.6.15
+====================
+
+1. The :ref:`VIDIOC_LOG_STATUS` ioctl was added.
+
+2. New video standards ``V4L2_STD_NTSC_443``, ``V4L2_STD_SECAM_LC``,
+   ``V4L2_STD_SECAM_DK`` (a set of SECAM D, K and K1), and
+   ``V4L2_STD_ATSC`` (a set of ``V4L2_STD_ATSC_8_VSB`` and
+   ``V4L2_STD_ATSC_16_VSB``) were defined. Note the ``V4L2_STD_525_60``
+   set now includes ``V4L2_STD_NTSC_443``. See also
+   :ref:`v4l2-std-id`.
+
+3. The ``VIDIOC_G_COMP`` and ``VIDIOC_S_COMP`` ioctl were renamed to
+   ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` respectively. Their
+   argument was replaced by a struct
+   ``v4l2_mpeg_compression`` pointer. (The
+   ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls where removed
+   in Linux 2.6.25.)
+
+V4L2 spec erratum 2005-11-27
+============================
+
+The capture example in :ref:`capture-example` called the
+:ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctl without checking if
+cropping is supported. In the video standard selection example in
+:ref:`standard` the :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` call used
+the wrong argument type.
+
+V4L2 spec erratum 2006-01-10
+============================
+
+1. The ``V4L2_IN_ST_COLOR_KILL`` flag in struct v4l2_input not only
+   indicates if the color killer is enabled, but also if it is active.
+   (The color killer disables color decoding when it detects no color
+   in the video signal to improve the image quality.)
+
+2. :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` is a write-read ioctl, not
+   write-only as stated on its reference page. The ioctl changed in 2003
+   as noted above.
+
+V4L2 spec erratum 2006-02-03
+============================
+
+1. In struct v4l2_captureparm and struct v4l2_outputparm the ``timeperframe``
+   field gives the time in seconds, not microseconds.
+
+V4L2 spec erratum 2006-02-04
+============================
+
+1. The ``clips`` field in struct v4l2_window
+   must point to an array of struct v4l2_clip, not
+   a linked list, because drivers ignore the
+   struct v4l2_clip. ``next`` pointer.
+
+V4L2 in Linux 2.6.17
+====================
+
+1. New video standard macros were added: ``V4L2_STD_NTSC_M_KR`` (NTSC M
+   South Korea), and the sets ``V4L2_STD_MN``, ``V4L2_STD_B``,
+   ``V4L2_STD_GH`` and ``V4L2_STD_DK``. The ``V4L2_STD_NTSC`` and
+   ``V4L2_STD_SECAM`` sets now include ``V4L2_STD_NTSC_M_KR`` and
+   ``V4L2_STD_SECAM_LC`` respectively.
+
+2. A new ``V4L2_TUNER_MODE_LANG1_LANG2`` was defined to record both
+   languages of a bilingual program. The use of
+   ``V4L2_TUNER_MODE_STEREO`` for this purpose is deprecated now. See
+   the :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` section for details.
+
+V4L2 spec erratum 2006-09-23 (Draft 0.15)
+=========================================
+
+1. In various places ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE`` and
+   ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT`` of the sliced VBI interface were
+   not mentioned along with other buffer types.
+
+2. In :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` it was clarified that the
+   struct v4l2_audio ``mode`` field is a flags field.
+
+3. :ref:`VIDIOC_QUERYCAP` did not mention the sliced VBI and radio
+   capability flags.
+
+4. In :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` it was clarified that
+   applications must initialize the tuner ``type`` field of
+   struct v4l2_frequency before calling
+   :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>`.
+
+5. The ``reserved`` array in struct v4l2_requestbuffers has 2 elements,
+   not 32.
+
+6. In :ref:`output` and :ref:`raw-vbi` the device file names
+   ``/dev/vout`` which never caught on were replaced by ``/dev/video``.
+
+7. With Linux 2.6.15 the possible range for VBI device minor numbers was
+   extended from 224-239 to 224-255. Accordingly device file names
+   ``/dev/vbi0`` to ``/dev/vbi31`` are possible now.
+
+V4L2 in Linux 2.6.18
+====================
+
+1. New ioctls :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
+   :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and
+   :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` were added, a
+   flag to skip unsupported controls with
+   :ref:`VIDIOC_QUERYCTRL`, new control types
+   ``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_TYPE_CTRL_CLASS``
+   (enum v4l2_ctrl_type), and new control flags
+   ``V4L2_CTRL_FLAG_READ_ONLY``, ``V4L2_CTRL_FLAG_UPDATE``,
+   ``V4L2_CTRL_FLAG_INACTIVE`` and ``V4L2_CTRL_FLAG_SLIDER``
+   (:ref:`control-flags`). See :ref:`extended-controls` for details.
+
+V4L2 in Linux 2.6.19
+====================
+
+1. In struct v4l2_sliced_vbi_cap a
+   buffer type field was added replacing a reserved field. Note on
+   architectures where the size of enum types differs from int types the
+   size of the structure changed. The
+   :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl
+   was redefined from being read-only to write-read. Applications must
+   initialize the type field and clear the reserved fields now. These
+   changes may *break the compatibility* with older drivers and
+   applications.
+
+2. The ioctls :ref:`VIDIOC_ENUM_FRAMESIZES`
+   and
+   :ref:`VIDIOC_ENUM_FRAMEINTERVALS`
+   were added.
+
+3. A new pixel format ``V4L2_PIX_FMT_RGB444`` (:ref:`pixfmt-rgb`) was
+   added.
+
+V4L2 spec erratum 2006-10-12 (Draft 0.17)
+=========================================
+
+1. ``V4L2_PIX_FMT_HM12`` (:ref:`reserved-formats`) is a YUV 4:2:0, not
+   4:2:2 format.
+
+V4L2 in Linux 2.6.21
+====================
+
+1. The ``videodev2.h`` header file is now dual licensed under GNU
+   General Public License version two or later, and under a 3-clause
+   BSD-style license.
+
+V4L2 in Linux 2.6.22
+====================
+
+1. Two new field orders ``V4L2_FIELD_INTERLACED_TB`` and
+   ``V4L2_FIELD_INTERLACED_BT`` were added. See enum v4l2_field for
+   details.
+
+2. Three new clipping/blending methods with a global or straight or
+   inverted local alpha value were added to the video overlay interface.
+   See the description of the :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`
+   and :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` ioctls for details.
+
+   A new ``global_alpha`` field was added to struct v4l2_window,
+   extending the structure. This may **break compatibility** with
+   applications using a struct v4l2_window directly. However the
+   :ref:`VIDIOC_G/S/TRY_FMT <VIDIOC_G_FMT>` ioctls, which take a
+   pointer to a struct v4l2_format parent structure
+   with padding bytes at the end, are not affected.
+
+3. The format of the ``chromakey`` field in struct v4l2_window changed from
+   "host order RGB32" to a pixel value in the same format as the framebuffer.
+   This may **break compatibility** with existing applications. Drivers
+   supporting the "host order RGB32" format are not known.
+
+V4L2 in Linux 2.6.24
+====================
+
+1. The pixel formats ``V4L2_PIX_FMT_PAL8``, ``V4L2_PIX_FMT_YUV444``,
+   ``V4L2_PIX_FMT_YUV555``, ``V4L2_PIX_FMT_YUV565`` and
+   ``V4L2_PIX_FMT_YUV32`` were added.
+
+V4L2 in Linux 2.6.25
+====================
+
+1. The pixel formats :ref:`V4L2_PIX_FMT_Y16 <V4L2-PIX-FMT-Y16>` and
+   :ref:`V4L2_PIX_FMT_SBGGR16 <V4L2-PIX-FMT-SBGGR16>` were added.
+
+2. New :ref:`controls <control>` ``V4L2_CID_POWER_LINE_FREQUENCY``,
+   ``V4L2_CID_HUE_AUTO``, ``V4L2_CID_WHITE_BALANCE_TEMPERATURE``,
+   ``V4L2_CID_SHARPNESS`` and ``V4L2_CID_BACKLIGHT_COMPENSATION`` were
+   added. The controls ``V4L2_CID_BLACK_LEVEL``, ``V4L2_CID_WHITENESS``,
+   ``V4L2_CID_HCENTER`` and ``V4L2_CID_VCENTER`` were deprecated.
+
+3. A :ref:`Camera controls class <camera-controls>` was added, with
+   the new controls ``V4L2_CID_EXPOSURE_AUTO``,
+   ``V4L2_CID_EXPOSURE_ABSOLUTE``, ``V4L2_CID_EXPOSURE_AUTO_PRIORITY``,
+   ``V4L2_CID_PAN_RELATIVE``, ``V4L2_CID_TILT_RELATIVE``,
+   ``V4L2_CID_PAN_RESET``, ``V4L2_CID_TILT_RESET``,
+   ``V4L2_CID_PAN_ABSOLUTE``, ``V4L2_CID_TILT_ABSOLUTE``,
+   ``V4L2_CID_FOCUS_ABSOLUTE``, ``V4L2_CID_FOCUS_RELATIVE`` and
+   ``V4L2_CID_FOCUS_AUTO``.
+
+4. The ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls, which
+   were superseded by the :ref:`extended controls <extended-controls>`
+   interface in Linux 2.6.18, where finally removed from the
+   ``videodev2.h`` header file.
+
+V4L2 in Linux 2.6.26
+====================
+
+1. The pixel formats ``V4L2_PIX_FMT_Y16`` and ``V4L2_PIX_FMT_SBGGR16``
+   were added.
+
+2. Added user controls ``V4L2_CID_CHROMA_AGC`` and
+   ``V4L2_CID_COLOR_KILLER``.
+
+V4L2 in Linux 2.6.27
+====================
+
+1. The :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
+   and the ``V4L2_CAP_HW_FREQ_SEEK`` capability were added.
+
+2. The pixel formats ``V4L2_PIX_FMT_YVYU``, ``V4L2_PIX_FMT_PCA501``,
+   ``V4L2_PIX_FMT_PCA505``, ``V4L2_PIX_FMT_PCA508``,
+   ``V4L2_PIX_FMT_PCA561``, ``V4L2_PIX_FMT_SGBRG8``,
+   ``V4L2_PIX_FMT_PAC207`` and ``V4L2_PIX_FMT_PJPG`` were added.
+
+V4L2 in Linux 2.6.28
+====================
+
+1. Added ``V4L2_MPEG_AUDIO_ENCODING_AAC`` and
+   ``V4L2_MPEG_AUDIO_ENCODING_AC3`` MPEG audio encodings.
+
+2. Added ``V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC`` MPEG video encoding.
+
+3. The pixel formats ``V4L2_PIX_FMT_SGRBG10`` and
+   ``V4L2_PIX_FMT_SGRBG10DPCM8`` were added.
+
+V4L2 in Linux 2.6.29
+====================
+
+1. The ``VIDIOC_G_CHIP_IDENT`` ioctl was renamed to
+   ``VIDIOC_G_CHIP_IDENT_OLD`` and ``VIDIOC_DBG_G_CHIP_IDENT`` was
+   introduced in its place. The old struct ``v4l2_chip_ident`` was renamed to
+   struct ``v4l2_chip_ident_old``.
+
+2. The pixel formats ``V4L2_PIX_FMT_VYUY``, ``V4L2_PIX_FMT_NV16`` and
+   ``V4L2_PIX_FMT_NV61`` were added.
+
+3. Added camera controls ``V4L2_CID_ZOOM_ABSOLUTE``,
+   ``V4L2_CID_ZOOM_RELATIVE``, ``V4L2_CID_ZOOM_CONTINUOUS`` and
+   ``V4L2_CID_PRIVACY``.
+
+V4L2 in Linux 2.6.30
+====================
+
+1. New control flag ``V4L2_CTRL_FLAG_WRITE_ONLY`` was added.
+
+2. New control ``V4L2_CID_COLORFX`` was added.
+
+V4L2 in Linux 2.6.32
+====================
+
+1. In order to be easier to compare a V4L2 API and a kernel version, now
+   V4L2 API is numbered using the Linux Kernel version numeration.
+
+2. Finalized the RDS capture API. See :ref:`rds` for more information.
+
+3. Added new capabilities for modulators and RDS encoders.
+
+4. Add description for libv4l API.
+
+5. Added support for string controls via new type
+   ``V4L2_CTRL_TYPE_STRING``.
+
+6. Added ``V4L2_CID_BAND_STOP_FILTER`` documentation.
+
+7. Added FM Modulator (FM TX) Extended Control Class:
+   ``V4L2_CTRL_CLASS_FM_TX`` and their Control IDs.
+
+8. Added FM Receiver (FM RX) Extended Control Class:
+   ``V4L2_CTRL_CLASS_FM_RX`` and their Control IDs.
+
+9. Added Remote Controller chapter, describing the default Remote
+   Controller mapping for media devices.
+
+V4L2 in Linux 2.6.33
+====================
+
+1. Added support for Digital Video timings in order to support HDTV
+   receivers and transmitters.
+
+V4L2 in Linux 2.6.34
+====================
+
+1. Added ``V4L2_CID_IRIS_ABSOLUTE`` and ``V4L2_CID_IRIS_RELATIVE``
+   controls to the :ref:`Camera controls class <camera-controls>`.
+
+V4L2 in Linux 2.6.37
+====================
+
+1. Remove the vtx (videotext/teletext) API. This API was no longer used
+   and no hardware exists to verify the API. Nor were any userspace
+   applications found that used it. It was originally scheduled for
+   removal in 2.6.35.
+
+V4L2 in Linux 2.6.39
+====================
+
+1. The old VIDIOC_*_OLD symbols and V4L1 support were removed.
+
+2. Multi-planar API added. Does not affect the compatibility of current
+   drivers and applications. See :ref:`multi-planar API <planar-apis>`
+   for details.
+
+V4L2 in Linux 3.1
+=================
+
+1. VIDIOC_QUERYCAP now returns a per-subsystem version instead of a
+   per-driver one.
+
+   Standardize an error code for invalid ioctl.
+
+   Added V4L2_CTRL_TYPE_BITMASK.
+
+V4L2 in Linux 3.2
+=================
+
+1. V4L2_CTRL_FLAG_VOLATILE was added to signal volatile controls to
+   userspace.
+
+2. Add selection API for extended control over cropping and composing.
+   Does not affect the compatibility of current drivers and
+   applications. See :ref:`selection API <selection-api>` for details.
+
+V4L2 in Linux 3.3
+=================
+
+1. Added ``V4L2_CID_ALPHA_COMPONENT`` control to the
+   :ref:`User controls class <control>`.
+
+2. Added the device_caps field to struct v4l2_capabilities and added
+   the new V4L2_CAP_DEVICE_CAPS capability.
+
+V4L2 in Linux 3.4
+=================
+
+1. Added :ref:`JPEG compression control class <jpeg-controls>`.
+
+2. Extended the DV Timings API:
+   :ref:`VIDIOC_ENUM_DV_TIMINGS`,
+   :ref:`VIDIOC_QUERY_DV_TIMINGS` and
+   :ref:`VIDIOC_DV_TIMINGS_CAP`.
+
+V4L2 in Linux 3.5
+=================
+
+1. Added integer menus, the new type will be
+   V4L2_CTRL_TYPE_INTEGER_MENU.
+
+2. Added selection API for V4L2 subdev interface:
+   :ref:`VIDIOC_SUBDEV_G_SELECTION` and
+   :ref:`VIDIOC_SUBDEV_S_SELECTION <VIDIOC_SUBDEV_G_SELECTION>`.
+
+3. Added ``V4L2_COLORFX_ANTIQUE``, ``V4L2_COLORFX_ART_FREEZE``,
+   ``V4L2_COLORFX_AQUA``, ``V4L2_COLORFX_SILHOUETTE``,
+   ``V4L2_COLORFX_SOLARIZATION``, ``V4L2_COLORFX_VIVID`` and
+   ``V4L2_COLORFX_ARBITRARY_CBCR`` menu items to the
+   ``V4L2_CID_COLORFX`` control.
+
+4. Added ``V4L2_CID_COLORFX_CBCR`` control.
+
+5. Added camera controls ``V4L2_CID_AUTO_EXPOSURE_BIAS``,
+   ``V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE``,
+   ``V4L2_CID_IMAGE_STABILIZATION``, ``V4L2_CID_ISO_SENSITIVITY``,
+   ``V4L2_CID_ISO_SENSITIVITY_AUTO``, ``V4L2_CID_EXPOSURE_METERING``,
+   ``V4L2_CID_SCENE_MODE``, ``V4L2_CID_3A_LOCK``,
+   ``V4L2_CID_AUTO_FOCUS_START``, ``V4L2_CID_AUTO_FOCUS_STOP``,
+   ``V4L2_CID_AUTO_FOCUS_STATUS`` and ``V4L2_CID_AUTO_FOCUS_RANGE``.
+
+V4L2 in Linux 3.6
+=================
+
+1. Replaced ``input`` in struct v4l2_buffer by
+   ``reserved2`` and removed ``V4L2_BUF_FLAG_INPUT``.
+
+2. Added V4L2_CAP_VIDEO_M2M and V4L2_CAP_VIDEO_M2M_MPLANE
+   capabilities.
+
+3. Added support for frequency band enumerations:
+   :ref:`VIDIOC_ENUM_FREQ_BANDS`.
+
+V4L2 in Linux 3.9
+=================
+
+1. Added timestamp types to ``flags`` field in
+   struct v4l2_buffer. See :ref:`buffer-flags`.
+
+2. Added ``V4L2_EVENT_CTRL_CH_RANGE`` control event changes flag. See
+   :ref:`ctrl-changes-flags`.
+
+V4L2 in Linux 3.10
+==================
+
+1. Removed obsolete and unused DV_PRESET ioctls VIDIOC_G_DV_PRESET,
+   VIDIOC_S_DV_PRESET, VIDIOC_QUERY_DV_PRESET and
+   VIDIOC_ENUM_DV_PRESET. Remove the related v4l2_input/output
+   capability flags V4L2_IN_CAP_PRESETS and V4L2_OUT_CAP_PRESETS.
+
+2. Added new debugging ioctl
+   :ref:`VIDIOC_DBG_G_CHIP_INFO`.
+
+V4L2 in Linux 3.11
+==================
+
+1. Remove obsolete ``VIDIOC_DBG_G_CHIP_IDENT`` ioctl.
+
+V4L2 in Linux 3.14
+==================
+
+1. In struct v4l2_rect, the type of ``width`` and
+   ``height`` fields changed from _s32 to _u32.
+
+V4L2 in Linux 3.15
+==================
+
+1. Added Software Defined Radio (SDR) Interface.
+
+V4L2 in Linux 3.16
+==================
+
+1. Added event V4L2_EVENT_SOURCE_CHANGE.
+
+V4L2 in Linux 3.17
+==================
+
+1. Extended struct v4l2_pix_format. Added
+   format flags.
+
+2. Added compound control types and
+   :ref:`VIDIOC_QUERY_EXT_CTRL <VIDIOC_QUERYCTRL>`.
+
+V4L2 in Linux 3.18
+==================
+
+1. Added ``V4L2_CID_PAN_SPEED`` and ``V4L2_CID_TILT_SPEED`` camera
+   controls.
+
+V4L2 in Linux 3.19
+==================
+
+1. Rewrote Colorspace chapter, added new enum v4l2_ycbcr_encoding
+   and enum v4l2_quantization fields to struct v4l2_pix_format,
+   struct v4l2_pix_format_mplane and struct v4l2_mbus_framefmt.
+
+V4L2 in Linux 4.4
+=================
+
+1. Renamed ``V4L2_TUNER_ADC`` to ``V4L2_TUNER_SDR``. The use of
+   ``V4L2_TUNER_ADC`` is deprecated now.
+
+2. Added ``V4L2_CID_RF_TUNER_RF_GAIN`` RF Tuner control.
+
+3. Added transmitter support for Software Defined Radio (SDR) Interface.
+
+.. _other:
+
+Relation of V4L2 to other Linux multimedia APIs
+===============================================
+
+.. _xvideo:
+
+X Video Extension
+-----------------
+
+The X Video Extension (abbreviated XVideo or just Xv) is an extension of
+the X Window system, implemented for example by the XFree86 project. Its
+scope is similar to V4L2, an API to video capture and output devices for
+X clients. Xv allows applications to display live video in a window,
+send window contents to a TV output, and capture or output still images
+in XPixmaps [#f1]_. With their implementation XFree86 makes the extension
+available across many operating systems and architectures.
+
+Because the driver is embedded into the X server Xv has a number of
+advantages over the V4L2 :ref:`video overlay interface <overlay>`. The
+driver can easily determine the overlay target, i. e. visible graphics
+memory or off-screen buffers for a destructive overlay. It can program
+the RAMDAC for a non-destructive overlay, scaling or color-keying, or
+the clipping functions of the video capture hardware, always in sync
+with drawing operations or windows moving or changing their stacking
+order.
+
+To combine the advantages of Xv and V4L a special Xv driver exists in
+XFree86 and XOrg, just programming any overlay capable Video4Linux
+device it finds. To enable it ``/etc/X11/XF86Config`` must contain these
+lines:
+
+::
+
+    Section "Module"
+	Load "v4l"
+    EndSection
+
+As of XFree86 4.2 this driver still supports only V4L ioctls, however it
+should work just fine with all V4L2 devices through the V4L2
+backward-compatibility layer. Since V4L2 permits multiple opens it is
+possible (if supported by the V4L2 driver) to capture video while an X
+client requested video overlay. Restrictions of simultaneous capturing
+and overlay are discussed in :ref:`overlay` apply.
+
+Only marginally related to V4L2, XFree86 extended Xv to support hardware
+YUV to RGB conversion and scaling for faster video playback, and added
+an interface to MPEG-2 decoding hardware. This API is useful to display
+images captured with V4L2 devices.
+
+Digital Video
+-------------
+
+V4L2 does not support digital terrestrial, cable or satellite broadcast.
+A separate project aiming at digital receivers exists. You can find its
+homepage at `https://linuxtv.org <https://linuxtv.org>`__. The Linux
+DVB API has no connection to the V4L2 API except that drivers for hybrid
+hardware may support both.
+
+Audio Interfaces
+----------------
+
+[to do - OSS/ALSA]
+
+.. _experimental:
+
+Experimental API Elements
+=========================
+
+The following V4L2 API elements are currently experimental and may
+change in the future.
+
+-  :ref:`VIDIOC_DBG_G_REGISTER` and
+   :ref:`VIDIOC_DBG_S_REGISTER <VIDIOC_DBG_G_REGISTER>` ioctls.
+
+-  :ref:`VIDIOC_DBG_G_CHIP_INFO` ioctl.
+
+.. _obsolete:
+
+Obsolete API Elements
+=====================
+
+The following V4L2 API elements were superseded by new interfaces and
+should not be implemented in new drivers.
+
+-  ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls. Use Extended
+   Controls, :ref:`extended-controls`.
+
+-  VIDIOC_G_DV_PRESET, VIDIOC_S_DV_PRESET,
+   VIDIOC_ENUM_DV_PRESETS and VIDIOC_QUERY_DV_PRESET ioctls. Use
+   the DV Timings API (:ref:`dv-timings`).
+
+-  ``VIDIOC_SUBDEV_G_CROP`` and ``VIDIOC_SUBDEV_S_CROP`` ioctls. Use
+   ``VIDIOC_SUBDEV_G_SELECTION`` and ``VIDIOC_SUBDEV_S_SELECTION``,
+   :ref:`VIDIOC_SUBDEV_G_SELECTION`.
+
+.. [#f1]
+   This is not implemented in XFree86.