diff options
| author | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2009-12-09 08:39:58 -0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2011-03-22 04:53:09 -0300 |
| commit | 176fb0d108f7495ccf9aa127e1342a1a0d87e004 (patch) | |
| tree | a1b54ad186dde663853d4d2d24f42cd7c0f94bfb /Documentation/DocBook/v4l | |
| parent | cf4b9211b5680cd9ca004232e517fb7ec5bf5316 (diff) | |
[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>
Diffstat (limited to 'Documentation/DocBook/v4l')
| -rw-r--r-- | Documentation/DocBook/v4l/media-controller.xml | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/Documentation/DocBook/v4l/media-controller.xml b/Documentation/DocBook/v4l/media-controller.xml new file mode 100644 index 000000000000..253ddb4426c9 --- /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> |