1 .. SPDX-License-Identifier: GFDL-1.1-no-invari !! 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
2 9
3 .. _media-controller-model: 10 .. _media-controller-model:
4 11
5 Media device model 12 Media device model
6 ================== 13 ==================
7 14
8 Discovering a device internal topology, and co 15 Discovering a device internal topology, and configuring it at runtime,
9 is one of the goals of the media controller AP 16 is one of the goals of the media controller API. To achieve this,
10 hardware devices and Linux Kernel interfaces a 17 hardware devices and Linux Kernel interfaces are modelled as graph
11 objects on an oriented graph. The object types 18 objects on an oriented graph. The object types that constitute the graph
12 are: 19 are:
13 20
14 - An **entity** is a basic media hardware or 21 - An **entity** is a basic media hardware or software building block.
15 It can correspond to a large variety of log 22 It can correspond to a large variety of logical blocks such as
16 physical hardware devices (CMOS sensor for 23 physical hardware devices (CMOS sensor for instance), logical
17 hardware devices (a building block in a Sys 24 hardware devices (a building block in a System-on-Chip image
18 processing pipeline), DMA channels or physi 25 processing pipeline), DMA channels or physical connectors.
19 26
20 - An **interface** is a graph representation 27 - An **interface** is a graph representation of a Linux Kernel
21 userspace API interface, like a device node 28 userspace API interface, like a device node or a sysfs file that
22 controls one or more entities in the graph. 29 controls one or more entities in the graph.
23 30
24 - A **pad** is a data connection endpoint thr 31 - A **pad** is a data connection endpoint through which an entity can
25 interact with other entities. Data (not res 32 interact with other entities. Data (not restricted to video) produced
26 by an entity flows from the entity's output 33 by an entity flows from the entity's output to one or more entity
27 inputs. Pads should not be confused with ph 34 inputs. Pads should not be confused with physical pins at chip
28 boundaries. 35 boundaries.
29 36
30 - A **data link** is a point-to-point oriente 37 - A **data link** is a point-to-point oriented connection between two
31 pads, either on the same entity or on diffe 38 pads, either on the same entity or on different entities. Data flows
32 from a source pad to a sink pad. 39 from a source pad to a sink pad.
33 40
34 - An **interface link** is a point-to-point b 41 - An **interface link** is a point-to-point bidirectional control
35 connection between a Linux Kernel interface 42 connection between a Linux Kernel interface and an entity.
36 <<
37 - An **ancillary link** is a point-to-point co <<
38 entities form a single logical unit. For exa <<
39 fact that a particular camera sensor and len <<
40 physical module, meaning this lens controlle <<
41 camera sensor. <<
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