Merge tag 'media/v4.8-4' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media

Pull media documentation updates from Mauro Carvalho Chehab:
 "This patch series does the conversion of all media documentation stuff
  to Restrutured Text markup format and add them to the
  Documentation/index.rst file.

  The media documentation was grouped into 4 books:

    - media uAPI
    - media kAPI
    - V4L driver-specific documentation
    - DVB driver-specific documentation

  It also contains several documentation improvements and one fixup
  patch for a core issue with cropcap.

  PS.  After this patch series, the media DocBook is deprecated and
  should be removed.  I'll add such patch on a future pull request"

* tag 'media/v4.8-4' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (322 commits)
  [media] cx23885-cardlist.rst: add a new card
  [media] doc-rst: add some needed escape codes
  [media] doc-rst: kapi: use :c:func: instead of :cpp:func
  doc-rst: kernel-doc: fix a change introduced by mistake
  [media] v4l2-ioctl.h add debug info for struct v4l2_ioctl_ops
  [media] dvb_ringbuffer.h: some documentation improvements
  [media] v4l2-ctrls.h: fully document the header file
  [media] doc-rst: Fix some typedef ugly warnings
  [media] doc-rst: reorganize the kAPI v4l2 chapters
  [media] rename v4l2-framework.rst to v4l2-intro.rst
  [media] move V4L2 clocks to a separate .rst file
  [media] v4l2-fh.rst: add cross references and markups
  [media] v4l2-fh.rst: add fh contents from v4l2-framework.rst
  [media] v4l2-fh.h: add documentation for it
  [media] v4l2-event.rst: add cross-references and markups
  [media] v4l2-event.h: document all functions
  [media] v4l2-event.rst: add text from v4l2-framework.rst
  [media] v4l2-framework.rst: remove videobuf quick chapter
  [media] v4l2-dev: add cross-references and improve markup
  [media] doc-rst: move v4l2-dev doc to a separate file
  ...

1 files changed, 104 insertions, 0 deletions

diff --git a/Documentation/media/uapi/v4l/dev-capture.rst b/Documentation/media/uapi/v4l/dev-capture.rst
new file mode 100644
index 000000000000..8d049471e1c2
--- /dev/null
+++ b/Documentation/media/uapi/v4l/dev-capture.rst
@@ -0,0 +1,104 @@
+.. -*- coding: utf-8; mode: rst -*-
+
+.. _capture:
+
+***********************
+Video Capture Interface
+***********************
+
+Video capture devices sample an analog video signal and store the
+digitized images in memory. Today nearly all devices can capture at full
+25 or 30 frames/second. With this interface applications can control the
+capture process and move images from the driver into user space.
+
+Conventionally V4L2 video capture devices are accessed through character
+device special files named ``/dev/video`` and ``/dev/video0`` to
+``/dev/video63`` with major number 81 and minor numbers 0 to 63.
+``/dev/video`` is typically a symbolic link to the preferred video
+device.
+
+.. note:: The same device file names are used for video output devices.
+
+
+Querying Capabilities
+=====================
+
+Devices supporting the video capture interface set the
+``V4L2_CAP_VIDEO_CAPTURE`` or ``V4L2_CAP_VIDEO_CAPTURE_MPLANE`` flag in
+the ``capabilities`` field of struct
+:ref:`v4l2_capability <v4l2-capability>` returned by the
+:ref:`VIDIOC_QUERYCAP` ioctl. As secondary device
+functions they may also support the :ref:`video overlay <overlay>`
+(``V4L2_CAP_VIDEO_OVERLAY``) and the :ref:`raw VBI capture <raw-vbi>`
+(``V4L2_CAP_VBI_CAPTURE``) interface. At least one of the read/write or
+streaming I/O methods must be supported. Tuners and audio inputs are
+optional.
+
+
+Supplemental Functions
+======================
+
+Video capture devices shall support :ref:`audio input <audio>`,
+:ref:`tuner`, :ref:`controls <control>`,
+:ref:`cropping and scaling <crop>` and
+:ref:`streaming parameter <streaming-par>` ioctls as needed. The
+:ref:`video input <video>` and :ref:`video standard <standard>`
+ioctls must be supported by all video capture devices.
+
+
+Image Format Negotiation
+========================
+
+The result of a capture operation is determined by cropping and image
+format parameters. The former select an area of the video picture to
+capture, the latter how images are stored in memory, i. e. in RGB or YUV
+format, the number of bits per pixel or width and height. Together they
+also define how images are scaled in the process.
+
+As usual these parameters are *not* reset at :ref:`open() <func-open>`
+time to permit Unix tool chains, programming a device and then reading
+from it as if it was a plain file. Well written V4L2 applications ensure
+they really get what they want, including cropping and scaling.
+
+Cropping initialization at minimum requires to reset the parameters to
+defaults. An example is given in :ref:`crop`.
+
+To query the current image format applications set the ``type`` field of
+a struct :ref:`v4l2_format <v4l2-format>` to
+``V4L2_BUF_TYPE_VIDEO_CAPTURE`` or
+``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and call the
+:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctl with a pointer to this
+structure. Drivers fill the struct
+:ref:`v4l2_pix_format <v4l2-pix-format>` ``pix`` or the struct
+:ref:`v4l2_pix_format_mplane <v4l2-pix-format-mplane>` ``pix_mp``
+member of the ``fmt`` union.
+
+To request different parameters applications set the ``type`` field of a
+struct :ref:`v4l2_format <v4l2-format>` as above and initialize all
+fields of the struct :ref:`v4l2_pix_format <v4l2-pix-format>`
+``vbi`` member of the ``fmt`` union, or better just modify the results
+of :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`, and call the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`
+ioctl with a pointer to this structure. Drivers may adjust the
+parameters and finally return the actual parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`
+does.
+
+Like :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` the :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl
+can be used to learn about hardware limitations without disabling I/O or
+possibly time consuming hardware preparations.
+
+The contents of struct :ref:`v4l2_pix_format <v4l2-pix-format>` and
+struct :ref:`v4l2_pix_format_mplane <v4l2-pix-format-mplane>` are
+discussed in :ref:`pixfmt`. See also the specification of the
+:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`, :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` and :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctls for
+details. Video capture devices must implement both the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`
+and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl, even if :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ignores all
+requests and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does.
+:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is optional.
+
+
+Reading Images
+==============
+
+A video capture device may support the ::ref:`read() function <func-read>`
+and/or streaming (:ref:`memory mapping <func-mmap>` or
+:ref:`user pointer <userp>`) I/O. See :ref:`io` for details.