Introduction to DAPM, Linux Power Management for Embedded Audio Devices
summary
DAPM models audio hardware as a graph of widgets and routes and automatically powers only the widgets on active paths to cut wasted current and avoid pops by using ordered on/off sequences; drivers provide widget and route tables (often via regmap) or add them at probe time for different silicon revisions. Runtime inspection uses dapm debugfs files and visualizers: an older 50-line vis-dapm script and a new dandgraph shell tool (SSH remote mode) that successfully renders active-state graphs; ftrace shows the core’s compute/patch/power sequence.
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chapters (8)
- 0:00Introduction
- 1:03ALSA and sound card evolution
- 4:39What is DAPM
- 8:16DAPM widgets details
- 12:09Implementing DAPM in driver
- 20:36Inspecting DAPM state
- 26:41Debugging DAPM with ftrace
- 29:29Q&A
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