1.. Permission is granted to copy, distribute and/or modify this
2.. document under the terms of the GNU Free Documentation License,
3.. Version 1.1 or any later version published by the Free Software
4.. Foundation, with no Invariant Sections, no Front-Cover Texts
5.. and no Back-Cover Texts. A copy of the license is included at
6.. Documentation/userspace-api/media/fdl-appendix.rst.
7..
8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
9
10.. _media-controller-model:
11
12Media device model
13==================
14
15Discovering a device internal topology, and configuring it at runtime,
16is one of the goals of the media controller API. To achieve this,
17hardware devices and Linux Kernel interfaces are modelled as graph
18objects on an oriented graph. The object types that constitute the graph
19are:
20
21-  An **entity** is a basic media hardware or software building block.
22   It can correspond to a large variety of logical blocks such as
23   physical hardware devices (CMOS sensor for instance), logical
24   hardware devices (a building block in a System-on-Chip image
25   processing pipeline), DMA channels or physical connectors.
26
27-  An **interface** is a graph representation of a Linux Kernel
28   userspace API interface, like a device node or a sysfs file that
29   controls one or more entities in the graph.
30
31-  A **pad** is a data connection endpoint through which an entity can
32   interact with other entities. Data (not restricted to video) produced
33   by an entity flows from the entity's output to one or more entity
34   inputs. Pads should not be confused with physical pins at chip
35   boundaries.
36
37-  A **data link** is a point-to-point oriented connection between two
38   pads, either on the same entity or on different entities. Data flows
39   from a source pad to a sink pad.
40
41-  An **interface link** is a point-to-point bidirectional control
42   connection between a Linux Kernel interface and an entity.
43