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[media] DocBook: MC: add the concept of interfaces 

The Media Controller next generation patches added a new graph
element type: interfaces. It also allows links between interfaces
and entities. Update the docbook to reflect that.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This commit is contained in:
Mauro Carvalho Chehab 2015-12-12 08:59:14 -02:00
parent fdc40b5e95
commit b7870d692d
1 changed files with 26 additions and 14 deletions
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40
Documentation/DocBook/media/v4l/media-controller.xml
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@ -58,20 +58,32 @@
<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 are modelled as an oriented graph of building blocks called entities
connected through pads.</para>
<para>An entity 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>
<para>A pad is a 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>
<para>A link 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>
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>
</chapter>