[alsa-devel] amp power down event (resend with the correct email)

Peter Ujfalusi peter.ujfalusi at nokia.com
Tue Aug 10 12:42:16 CEST 2010


it is a good practice to CC the maintainers to get the attention (in this case 
Liam and Mark)..

On Monday 09 August 2010 21:05:53 ext Michael Trimarchi wrote:
> Hi all,
> I'm t rying to unde rstand when the event a re called.
> ...
> SND_SOC_DAPM_SPK("Front Speaker", amp_event),
> ...

This is turned on or off by the DAPM power sequences.
Take a look at the sound/soc/soc-dapm.c, and at the beginning of the file, you 
can see the on and off sequences.
The DAPM_SPK widget will be powered on last, and powered down first, or early to 
avoid the pop coming from other widget powering.

> My idea was:
> - set the mixe r
> - open st ream
> amp_event: event =>
> [  169.820558] ON
> - close st ream
> and receive the event => OFF. In the aplay example this happen
> afte r some seconds but in my application I don't receive the OFF
> event. What is w rong?

What do you mean? User space will not receive such an event, this is ASoC 
internal (specifically DAPM doing it's thing).
The some seconds you see is most likely 5 seconds, which is the soc delay for 
going lower power state after the stream has been stopped, or the loopback is 

> Michael


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