[alsa-devel] alsa device drain power

Michael Trimarchi trimarchi at gandalf.sssup.it
Fri Dec 18 11:03:27 CET 2009

Mark Brown wrote:
> On Thu, Dec 17, 2009 at 09:47:59AM +0100, Michael Trimarchi wrote:
>> I have a simple question is the general behavior that an alsa device 
>> start to drain power
>> when it starts to play sound or start to recording. What happen if there 
>> is an external amplifier
>> connect to sound device?
> In general any audio component is going to draw more power if there is a
> signal going through it than if it's idle.  This is true regardless of
> how the audio subsystem is split in terms of physical chips.
> What are you trying to find out here?
As reported by the datasheet the LM4853 has a bias circuitry shutdown.
This shutdown function is activated by applying a logic high to the
SHUTDOWN pin. This pin as command by the

static int lm4853_event(struct snd_soc_dapm_widget *w,
                        struct snd_kcontrol *k,
                        int event)

in gta02. I don't put any debug stuff there but I suppose
if I open the device with and asound.conf that set
the value to true of the Stereo Out this event is called. Is it right?


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