43 lines
1.9 KiB
ReStructuredText
43 lines
1.9 KiB
ReStructuredText
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.. Permission is granted to copy, distribute and/or modify this
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.. document under the terms of the GNU Free Documentation License,
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.. Version 1.1 or any later version published by the Free Software
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.. Foundation, with no Invariant Sections, no Front-Cover Texts
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.. and no Back-Cover Texts. A copy of the license is included at
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.. Documentation/media/uapi/fdl-appendix.rst.
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..
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.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
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.. _media-controller-model:
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Media device model
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==================
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Discovering a device internal topology, and configuring it at runtime,
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is one of the goals of the media controller API. To achieve this,
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hardware devices and Linux Kernel interfaces are modelled as graph
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objects on an oriented graph. The object types that constitute the graph
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are:
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- An **entity** is a basic media hardware or software building block.
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It can correspond to a large variety of logical blocks such as
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physical hardware devices (CMOS sensor for instance), logical
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hardware devices (a building block in a System-on-Chip image
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processing pipeline), DMA channels or physical connectors.
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- An **interface** is a graph representation of a Linux Kernel
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userspace API interface, like a device node or a sysfs file that
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controls one or more entities in the graph.
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- A **pad** is a data connection endpoint through which an entity can
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interact with other entities. Data (not restricted to video) produced
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by an entity flows from the entity's output to one or more entity
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inputs. Pads should not be confused with physical pins at chip
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boundaries.
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- A **data link** is a point-to-point oriented connection between two
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pads, either on the same entity or on different entities. Data flows
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from a source pad to a sink pad.
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- An **interface link** is a point-to-point bidirectional control
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connection between a Linux Kernel interface and an entity.
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