Report audio nodes to libsystemd

[JohnAmadis]

Summary

dmdevfs now also probes every node with DMDRVI_IOCTL_AUDIO_GET_INFO (dmdrvi 2.6). When the driver answers, the node is reported to libsystemd under the audio class, the same way display and input nodes are.

This lets any driver that implements the standard audio ioctls get its services started by device rules without reporting anything itself. Example: the WM8994 codec node from dmwm8994, /dev/wm8994:

[class=audio]
start=player@%name

Changes

• src/dmdevfs.c:
  • new DMDEVFS_REPORT_AUDIO bit, probed in probe_node_classes()
  • reported in report_node_added(), removed in report_node_removed()
  • accepted by report= and included in all
• include/dmdevfs.h: public DMDEVFS_CLASS_AUDIO ("audio").
• README.md: the reporting table and report= values.
• CMakeLists.txt: requires dmdrvi >= 2.6, the first release with the DMDRVI_IOCTL_AUDIO_* commands (the test modules too).

Nodes that don't answer the ioctl are not reported as audio, e.g. the dmsai stream node.

Tests

• The mock driver answers DMDRVI_IOCTL_AUDIO_GET_INFO when configured with audio=true.
• New fixture nodes mock6 (audio) and mock7 (audio, report=block), a [class=audio] rule and an aud@ unit.
• New step dmdevfs_reports_audio_nodes:
  • an audio node starts aud@<name> only under its own class
  • report=block suppresses it
  • display and plain nodes are not reported as audio
  • unmounting stops the unit

ctest: 9/9 passed locally, including test_dmdevfs 9/9 steps.

Related: choco-technologies/dmwm8994#3, choco-technologies/dmsai#7, choco-technologies/dmod-boot#122

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https://claude.ai/code/session_01Nr1HhezRY951yBxxTm1b65

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