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, 92 insertions, 0 deletions

diff --git a/Documentation/media/uapi/v4l/format.rst b/Documentation/media/uapi/v4l/format.rst
new file mode 100644
index 000000000000..7c73278849ca
--- /dev/null
+++ b/Documentation/media/uapi/v4l/format.rst
@@ -0,0 +1,92 @@
+.. -*- coding: utf-8; mode: rst -*-
+
+.. _format:
+
+************
+Data Formats
+************
+
+
+Data Format Negotiation
+=======================
+
+Different devices exchange different kinds of data with applications,
+for example video images, raw or sliced VBI data, RDS datagrams. Even
+within one kind many different formats are possible, in particular an
+abundance of image formats. Although drivers must provide a default and
+the selection persists across closing and reopening a device,
+applications should always negotiate a data format before engaging in
+data exchange. Negotiation means the application asks for a particular
+format and the driver selects and reports the best the hardware can do
+to satisfy the request. Of course applications can also just query the
+current selection.
+
+A single mechanism exists to negotiate all data formats using the
+aggregate struct :ref:`v4l2_format <v4l2-format>` and the
+:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
+:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls. Additionally the
+:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl can be used to examine
+what the hardware *could* do, without actually selecting a new data
+format. The data formats supported by the V4L2 API are covered in the
+respective device section in :ref:`devices`. For a closer look at
+image formats see :ref:`pixfmt`.
+
+The :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl is a major turning-point in the
+initialization sequence. Prior to this point multiple panel applications
+can access the same device concurrently to select the current input,
+change controls or modify other properties. The first :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`
+assigns a logical stream (video data, VBI data etc.) exclusively to one
+file descriptor.
+
+Exclusive means no other application, more precisely no other file
+descriptor, can grab this stream or change device properties
+inconsistent with the negotiated parameters. A video standard change for
+example, when the new standard uses a different number of scan lines,
+can invalidate the selected image format. Therefore only the file
+descriptor owning the stream can make invalidating changes. Accordingly
+multiple file descriptors which grabbed different logical streams
+prevent each other from interfering with their settings. When for
+example video overlay is about to start or already in progress,
+simultaneous video capturing may be restricted to the same cropping and
+image size.
+
+When applications omit the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl its locking side
+effects are implied by the next step, the selection of an I/O method
+with the :ref:`VIDIOC_REQBUFS` ioctl or implicit
+with the first :ref:`read() <func-read>` or
+:ref:`write() <func-write>` call.
+
+Generally only one logical stream can be assigned to a file descriptor,
+the exception being drivers permitting simultaneous video capturing and
+overlay using the same file descriptor for compatibility with V4L and
+earlier versions of V4L2. Switching the logical stream or returning into
+"panel mode" is possible by closing and reopening the device. Drivers
+*may* support a switch using :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`.
+
+All drivers exchanging data with applications must support the
+:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. Implementation of the
+:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is highly recommended but optional.
+
+
+Image Format Enumeration
+========================
+
+Apart of the generic format negotiation functions a special ioctl to
+enumerate all image formats supported by video capture, overlay or
+output devices is available. [#f1]_
+
+The :ref:`VIDIOC_ENUM_FMT` ioctl must be supported
+by all drivers exchanging image data with applications.
+
+    **Important**
+
+    Drivers are not supposed to convert image formats in kernel space.
+    They must enumerate only formats directly supported by the hardware.
+    If necessary driver writers should publish an example conversion
+    routine or library for integration into applications.
+
+.. [#f1]
+   Enumerating formats an application has no a-priori knowledge of
+   (otherwise it could explicitly ask for them and need not enumerate)
+   seems useless, but there are applications serving as proxy between
+   drivers and the actual video applications for which this is useful.