From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Trimarchi Subject: Re: alsa device drain power Date: Fri, 18 Dec 2009 11:03:27 +0100 Message-ID: <4B2B536F.4060800@gandalf.sssup.it> References: <4B29F03F.4020100@gandalf.sssup.it> <20091217110334.GB12245@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from panicking.kicks-ass.org (unknown [77.224.194.88]) by alsa0.perex.cz (Postfix) with ESMTP id B33A7103815 for ; Fri, 18 Dec 2009 11:03:47 +0100 (CET) In-Reply-To: <20091217110334.GB12245@sirena.org.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Mark Brown Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org 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? Michael