mikael-lovqvists-claude-agent
a29c556851
Modules (src/modules/): - common/error: App_Error struct with structured detail union, error codes, app_error_print(); designed for future upgrade to preprocessor-generated location codes - media_ctrl: media device enumeration, topology query (entities/pads/links), link enable/disable via Media Controller API (/dev/media*) - v4l2_ctrl: control enumeration (with menu item fetching), get/set via V4L2 ext controls API, device discovery (/dev/video*) All modules use -std=c11 -D_GNU_SOURCE, build artifacts go to build/ only. Kernel-version-dependent constants guarded with #ifdef + #warning. CLI drivers (dev/cli/): - media_ctrl_cli: list, info, topology, set-link subcommands - v4l2_ctrl_cli: list, controls, get, set subcommands Docs (docs/cli/): - media_ctrl_cli.md and v4l2_ctrl_cli.md with usage, examples, and context within the video routing system Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
3.0 KiB
media_ctrl_cli
A development tool for exploring and configuring the Linux Media Controller pipeline. It wraps the media_ctrl module and provides a command-line interface to the Media Controller API (/dev/media*).
This tool is the counterpart to media-ctl from the v4l-utils package. It covers the same ground but is built on our own media_ctrl translation unit.
Build
From the repository root:
make
Or from dev/cli/ directly:
make media_ctrl_cli
The binary is placed in dev/cli/.
Commands
list
Enumerate all media devices present on the system.
./media_ctrl_cli list
Example output:
Media devices:
/dev/media0
/dev/media1
info <device>
Show identification information for a media device.
./media_ctrl_cli info /dev/media0
Example output:
Device: /dev/media0
Driver: unicam
Model: unicam
Serial:
Bus info: platform:fe801000.csi
Media version: 5.15.0
Hardware rev: 0x00000000
Driver version: 5.15.0
topology <device>
Show the full pipeline topology: all entities, their pads, and all links between them. This is the main tool for understanding how a camera pipeline is structured.
./media_ctrl_cli topology /dev/media0
Example output on a Raspberry Pi with an IMX477 camera:
Device: unicam (/dev/media0)
Entity 1: imx477 4-001a
type: v4l2-subdev (0x00020001)
flags: 0x00000000
pads: 1 links: 1
pad 0: source
link: entity 1 pad 0 -> entity 2 pad 0 [enabled]
Entity 2: unicam-image
type: devnode (0x00010001)
flags: 0x00000000
pads: 1 links: 1
device: 81:1
pad 0: sink
link: entity 1 pad 0 -> entity 2 pad 0 [enabled]
Each entity shows:
- type — the kernel entity function code and its human-readable name
- pads — each pad with its direction (source or sink)
- links — connections to other entity pads, with enabled/disabled state and whether the link is immutable
set-link <device> <src_entity>:<src_pad> <sink_entity>:<sink_pad> <0|1>
Enable or disable a link between two pads. Entity IDs and pad indices are the numeric values shown in the topology output.
# Enable a link
./media_ctrl_cli set-link /dev/media0 1:0 2:0 1
# Disable a link
./media_ctrl_cli set-link /dev/media0 1:0 2:0 0
Immutable links cannot be changed and will return an error.
Relationship to the Video Routing System
media_ctrl_cli exercises the media_ctrl module, which is used in the video routing system for:
- Remote device enumeration — a connecting node can query the media topology of a remote host to discover available cameras before opening any streams
- Pipeline configuration — setting pad formats and enabling links is required before a V4L2 capture node can be used, particularly on platforms like the Raspberry Pi where the sensor and capture node are separate media entities
See also: v4l2_ctrl_cli.md for runtime camera parameter control.