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authorMauro Carvalho Chehab <mchehab@s-opensource.com>2016-07-27 11:32:31 +0200
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2016-07-29 01:08:19 +0200
commit43f71d93a0cb342f0c918fba3f6abb7661e40ad2 (patch)
treea1dc7288bc480e7027ca1827ca4876472fa12e40 /Documentation/DocBook/media/v4l/media-controller.xml
parentMerge tag 'media/v4.8-4' of git://git.kernel.org/pub/scm/linux/kernel/git/mch... (diff)
downloadlinux-43f71d93a0cb342f0c918fba3f6abb7661e40ad2.tar.xz
linux-43f71d93a0cb342f0c918fba3f6abb7661e40ad2.zip
doc-rst: Remove the media docbook
Now that all media documentation was converted to Sphinx, we should get rid of the old DocBook one, as we don't want people to submit patches against the old stuff. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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-<partinfo>
- <authorgroup>
- <author>
- <firstname>Laurent</firstname>
- <surname>Pinchart</surname>
- <affiliation><address><email>laurent.pinchart@ideasonboard.com</email></address></affiliation>
- <contrib>Initial version.</contrib>
- </author>
- </authorgroup>
- <copyright>
- <year>2010</year>
- <holder>Laurent Pinchart</holder>
- </copyright>
-
- <revhistory>
- <!-- Put document revisions here, newest first. -->
- <revision>
- <revnumber>1.0.0</revnumber>
- <date>2010-11-10</date>
- <authorinitials>lp</authorinitials>
- <revremark>Initial revision</revremark>
- </revision>
- </revhistory>
-</partinfo>
-
-<title>Media Controller API</title>
-
-<chapter id="media_controller">
- <title>Media Controller</title>
-
- <section id="media-controller-intro">
- <title>Introduction</title>
- <para>Media devices increasingly handle multiple related functions. Many USB
- cameras include microphones, video capture hardware can also output video,
- or SoC camera interfaces also perform memory-to-memory operations similar to
- video codecs.</para>
- <para>Independent functions, even when implemented in the same hardware, can
- be modelled as separate devices. A USB camera with a microphone will be
- presented to userspace applications as V4L2 and ALSA capture devices. The
- devices' relationships (when using a webcam, end-users shouldn't have to
- manually select the associated USB microphone), while not made available
- directly to applications by the drivers, can usually be retrieved from
- sysfs.</para>
- <para>With more and more advanced SoC devices being introduced, the current
- approach will not scale. Device topologies are getting increasingly complex
- and can't always be represented by a tree structure. Hardware blocks are
- shared between different functions, creating dependencies between seemingly
- unrelated devices.</para>
- <para>Kernel abstraction APIs such as V4L2 and ALSA provide means for
- applications to access hardware parameters. As newer hardware expose an
- increasingly high number of those parameters, drivers need to guess what
- applications really require based on limited information, thereby
- implementing policies that belong to userspace.</para>
- <para>The media controller API aims at solving those problems.</para>
- </section>
-
- <section id="media-controller-model">
- <title>Media device model</title>
- <para>Discovering a device internal topology, and configuring it at runtime,
- is one of the goals of the media controller API. To achieve this, hardware
- devices and Linux Kernel interfaces are modelled as graph objects on
- an oriented graph. The object types that constitute the graph are:</para>
- <itemizedlist>
- <listitem><para>An <emphasis role="bold">entity</emphasis>
- is a basic media hardware or software building block. It can correspond to
- a large variety of logical blocks such as physical hardware devices
- (CMOS sensor for instance), logical hardware devices (a building block in
- a System-on-Chip image processing pipeline), DMA channels or physical
- connectors.</para></listitem>
- <listitem><para>An <emphasis role="bold">interface</emphasis>
- is a graph representation of a Linux Kernel userspace API interface,
- like a device node or a sysfs file that controls one or more entities
- in the graph.</para></listitem>
- <listitem><para>A <emphasis role="bold">pad</emphasis>
- is a data connection endpoint through which an entity can interact with
- other entities. Data (not restricted to video) produced by an entity
- flows from the entity's output to one or more entity inputs. Pads should
- not be confused with physical pins at chip boundaries.</para></listitem>
- <listitem><para>A <emphasis role="bold">data link</emphasis>
- is a point-to-point oriented connection between two pads, either on the
- same entity or on different entities. Data flows from a source pad to a
- sink pad.</para></listitem>
- <listitem><para>An <emphasis role="bold">interface link</emphasis>
- is a point-to-point bidirectional control connection between a Linux
- Kernel interface and an entity.m</para></listitem>
- </itemizedlist>
- </section>
-
- <!-- All non-ioctl specific data types go here. -->
- &sub-media-types;
-</chapter>
-
-<appendix id="media-user-func">
- <title>Function Reference</title>
- <!-- Keep this alphabetically sorted. -->
- &sub-media-func-open;
- &sub-media-func-close;
- &sub-media-func-ioctl;
- <!-- All ioctls go here. -->
- &sub-media-ioc-device-info;
- &sub-media-ioc-g-topology;
- &sub-media-ioc-enum-entities;
- &sub-media-ioc-enum-links;
- &sub-media-ioc-setup-link;
-</appendix>