1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
3 .. _media-controller-model:
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
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.
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.
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
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.
34 - An **interface link** is a point-to-point bidirectional control
35 connection between a Linux Kernel interface and an entity.
37 - An **ancillary link** is a point-to-point connection denoting that two
38 entities form a single logical unit. For example this could represent the
39 fact that a particular camera sensor and lens controller form a single
40 physical module, meaning this lens controller drives the lens for this