sound/soc/dapm.rst

2 Dynamic Audio Power Management for Portable Devices
8 Dynamic Audio Power Management (DAPM) is designed to allow portable
9 Linux devices to use the minimum amount of power within the audio
10 subsystem at all times. It is independent of other kernel power
11 management frameworks and, as such, can easily co-exist with them.
16 switching decisions based upon any audio stream (capture/playback)
17 activity and audio mixer settings within the device.
21  * a **widget** is every part of the audio hardware that can be enabled by
27 audio routing graph. This graph is specific to each sound card and spans
32 The graph for the STM32MP1-DK1 sound card is shown in picture:
34 .. kernel-figure:: dapm-graph.svg
44       VREF, VMID (core codec and audio power)
57       audio subsystem signal paths
72 Audio DAPM widgets fall into a number of types:
101 	External regulator that supplies power to audio components.
103 	External clock that supplies clock to audio components.
105 	Audio Interface Input (with TDM slot mask).
107 	Audio Interface Output (with TDM slot mask).
111 	Digital Audio Interface Input.
113 	Digital Audio Interface Output.
121 	Inter widget audio data buffer within a DSP.
126 	Widget that performs an audio processing effect.
132 	Widget that encodes audio data from one format (usually PCM) to another
135 	Widget that decodes audio data from a compressed format to an
139 (Widgets are defined in include/sound/soc-dapm.h)
142 There are convenience macros defined in soc-dapm.h that can be used to quickly
150 ---------------------
179 -------------------
181 Path domain widgets have a ability to control or affect the audio signal or
182 audio paths within the audio subsystem. They have the following form:
208 ----------------------
212 machine audio component (non codec or DSP) that can be independently
234 -------------------
242 ---------------
244 Sometimes widgets exist in the codec or machine audio graph that don't have any
246 a virtual widget - a widget with no control bits e.g.
293 separate widgets and routes arrays implementing the case-specific features
302 audio paths (called interconnections). Each interconnection must be defined in
303 order to create a graph of all audio paths between widgets.
306 audio system), as it requires joining widgets together via their audio signal
317 name. We can now connect the destination widget (wrt audio signal) with its
345 -------------------------------
362 An endpoint is a start or end point (widget) of an audio signal within the
401 See soc-dapm.h for all other widgets that support events.
405 -----------
414   #define SND_SOC_DAPM_PRE_REG		0x10	/* before audio path setup */
415   #define SND_SOC_DAPM_POST_REG		0x20	/* after  audio path setup */