Merge branch 'topic/docs-next' into v4l_for_linus

* topic/docs-next: (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, 30 insertions, 0 deletions

diff --git a/Documentation/media/uapi/v4l/app-pri.rst b/Documentation/media/uapi/v4l/app-pri.rst
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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _app-pri:
+
+********************
+Application Priority
+********************
+
+When multiple applications share a device it may be desirable to assign
+them different priorities. Contrary to the traditional "rm -rf /" school
+of thought a video recording application could for example block other
+applications from changing video controls or switching the current TV
+channel. Another objective is to permit low priority applications
+working in background, which can be preempted by user controlled
+applications and automatically regain control of the device at a later
+time.
+
+Since these features cannot be implemented entirely in user space V4L2
+defines the :ref:`VIDIOC_G_PRIORITY <VIDIOC_G_PRIORITY>` and
+:ref:`VIDIOC_S_PRIORITY <VIDIOC_G_PRIORITY>` ioctls to request and
+query the access priority associate with a file descriptor. Opening a
+device assigns a medium priority, compatible with earlier versions of
+V4L2 and drivers not supporting these ioctls. Applications requiring a
+different priority will usually call :ref:`VIDIOC_S_PRIORITY
+<VIDIOC_G_PRIORITY>` after verifying the device with the
+:ref:`VIDIOC_QUERYCAP` ioctl.
+
+Ioctls changing driver properties, such as
+:ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>`, return an ``EBUSY`` error code
+after another application obtained higher priority.