sound/soc/dapm.rst

8 Dynamic Audio Power Management (DAPM) is designed to allow portable
9 Linux devices to use the minimum amount of power within the audio
11 such, can easily co-exist with the other PM systems.
13 DAPM is also completely transparent to all user space applications as
35       machine driver and responds to asynchronous events e.g when HP
51 routing map of the whole machine. This map is specific to each machine and
60 Audio DAPM widgets fall into a number of types:-
63 	Mixes several analog signals into a single analog signal.
65 	An analog switch that outputs only one of many inputs.
69 	Analog to Digital Converter
71 	Digital to Analog Converter
73 	An analog switch
89 	External regulator that supplies power to audio components.
91 	External clock that supplies clock to audio components.
99 	Digital Audio Interface Input.
101 	Digital Audio Interface Output.
120 	Widget that encodes audio data from one format (usually PCM) to another
123 	Widget that decodes audio data from a compressed format to an
127 (Widgets are defined in include/sound/soc-dapm.h)
129 Widgets can be added to the sound card by any of the component driver types.
130 There are convenience macros defined in soc-dapm.h that can be used to quickly
138 ---------------------
140 Stream Widgets relate to the stream power domain and only consist of ADCs
141 (analog to digital converters), DACs (digital to analog converters),
144 Stream widgets have the following format:-
167 -------------------
169 Path domain widgets have a ability to control or affect the audio signal or
170 audio paths within the audio subsystem. They have the following form:-
196 ----------------------
199 codec register bit associated with them. A machine widget is assigned to each
210 when the Mic is inserted:-::
222 -------------------
226 to any stream event or by kernel PM events.
230 ---------------
233 corresponding soft power control. In this case it is necessary to create
234 a virtual widget - a widget with no control bits e.g.
239 This can be used to merge to signal paths together in software.
241 After all the widgets have been defined, they can then be added to the DAPM
242 subsystem individually with a call to snd_soc_dapm_new_control().
248 Widgets are connected to each other within the codec, platform and machine by
250 order to create a map of all audio paths between widgets.
265 above) and is connected to the output mixer via its kcontrol name. We can now
274 So we have :-
278 * ``Output Mixer`` is connected to the ``DAC`` via the ``HiFi Playback Switch``.
283 Interconnections are created with a call to:-
289 interconnections have been registered with the core. This causes the core to
295 -------------------------------
297 directly connect the codec pins to machine level widgets.
299 e.g. connects the speaker out codec pins to the internal speaker.
302 	/* ext speaker connected to codec pins LOUT2, ROUT2  */
306 This allows the DAPM to power on and off pins that are connected (and in use)
321 Endpoints are added to the DAPM graph so that their usage can be determined in
322 order to save power. e.g. NC codecs pins will be switched OFF, unconnected
345 Please see soc-dapm.h for all other widgets that support events.
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