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