From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jarkko Nikula <jhnikula@gmail.com>
Subject: Re: question on dapm_reg_event()
Date: Wed, 6 Jan 2010 17:48:59 +0200
Message-ID: <20100106174859.227f1cd8.jhnikula@gmail.com>
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To: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: alsa-devel@alsa-project.org, Haojian Zhuang <haojian.zhuang@gmail.com>
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On Wed, 6 Jan 2010 14:53:22 +0000
Mark Brown <broonie@opensource.wolfsonmicro.com> wrote:

> On Mon, Jan 04, 2010 at 09:10:27PM -0500, Haojian Zhuang wrote:
> 
> > I just have a question on dapm code. In dapm_reg_event(), -(w->reg +
> > 1) is input parameter of snd_soc_update_bits(). Why we need to use
> > negative value as input parameter at here? Why do we not use w->reg at
> > here?
> 
> Hrm, no, that's not at all clear to me either.  CCing Jarkko who
> contributed the register write control originally.

IIRC, there were some reason to avoid register update by the
dapm_update_bits and negative register value was used to prevent it.

Reg+1 makes sure that the value is negative also for register 0.


-- 
Jarkko