[media] media: Media device
The media_device structure abstracts functions common to all kind of
media devices (v4l2, dvb, alsa, ...). It manages media entities and
offers a userspace API to discover and configure the media device
internal topology.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/Documentation/DocBook/media-entities.tmpl b/Documentation/DocBook/media-entities.tmpl
index d2f99e5..c47897f 100644
--- a/Documentation/DocBook/media-entities.tmpl
+++ b/Documentation/DocBook/media-entities.tmpl
@@ -327,6 +327,8 @@
<!ENTITY sub-media-entities SYSTEM "media-entities.tmpl">
<!ENTITY sub-media-indices SYSTEM "media-indices.tmpl">
+<!ENTITY sub-media-controller SYSTEM "v4l/media-controller.xml">
+
<!-- Function Reference -->
<!ENTITY close SYSTEM "v4l/func-close.xml">
<!ENTITY ioctl SYSTEM "v4l/func-ioctl.xml">
diff --git a/Documentation/DocBook/media.tmpl b/Documentation/DocBook/media.tmpl
index a99088a..88f2cc6 100644
--- a/Documentation/DocBook/media.tmpl
+++ b/Documentation/DocBook/media.tmpl
@@ -106,6 +106,9 @@
&sub-remote_controllers;
</chapter>
</part>
+<part id="media_common">
+&sub-media-controller;
+</part>
&sub-fdl-appendix;
diff --git a/Documentation/DocBook/v4l/media-controller.xml b/Documentation/DocBook/v4l/media-controller.xml
new file mode 100644
index 0000000..253ddb4
--- /dev/null
+++ b/Documentation/DocBook/v4l/media-controller.xml
@@ -0,0 +1,56 @@
+<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>
+</chapter>