[deliverable/linux.git] / Documentation / linux_tv / media / v4l / media-controller-model.rst

.. -*- coding: utf-8; mode: rst -*-

.. _media-controller-model:

Media device model
==================

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:

-  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.

-  An **interface** 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.

-  A **pad** 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.

-  A **data 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.

-  An **interface link** is a point-to-point bidirectional control
   connection between a Linux Kernel interface and an entity.m


.. ------------------------------------------------------------------------------
.. This file was automatically converted from DocBook-XML with the dbxml
.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
.. from the linux kernel, refer to:
..
.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
.. ------------------------------------------------------------------------------
Commit	Line	Data
5377d91f MH	1	.. -- coding: utf-8; mode: rst --
	2
	3	.. _media-controller-model:
	4
	5	Media device model
	6	==================
	7
	8	Discovering a device internal topology, and configuring it at runtime,
	9	is one of the goals of the media controller API. To achieve this,
	10	hardware devices and Linux Kernel interfaces are modelled as graph
	11	objects on an oriented graph. The object types that constitute the graph
	12	are:
	13
	14	- An entity is a basic media hardware or software building block.
	15	It can correspond to a large variety of logical blocks such as
	16	physical hardware devices (CMOS sensor for instance), logical
	17	hardware devices (a building block in a System-on-Chip image
	18	processing pipeline), DMA channels or physical connectors.
	19
	20	- An interface is a graph representation of a Linux Kernel
	21	userspace API interface, like a device node or a sysfs file that
	22	controls one or more entities in the graph.
	23
	24	- A pad is a data connection endpoint through which an entity can
	25	interact with other entities. Data (not restricted to video) produced
	26	by an entity flows from the entity's output to one or more entity
	27	inputs. Pads should not be confused with physical pins at chip
	28	boundaries.
	29
	30	- A data link is a point-to-point oriented connection between two
	31	pads, either on the same entity or on different entities. Data flows
	32	from a source pad to a sink pad.
	33
	34	- An interface link is a point-to-point bidirectional control
	35	connection between a Linux Kernel interface and an entity.m
	36
	37
	38	.. ------------------------------------------------------------------------------
	39	.. This file was automatically converted from DocBook-XML with the dbxml
	40	.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
	41	.. from the linux kernel, refer to:
	42	..
	43	.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
	44	.. ------------------------------------------------------------------------------