From: Jarkko Nikula <jhnikula@gmail.com>
To: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: alsa-devel@alsa-project.org, Haojian Zhuang <haojian.zhuang@gmail.com>
Subject: Re: question on dapm_reg_event()
Date: Wed, 6 Jan 2010 17:48:59 +0200 [thread overview]
Message-ID: <20100106174859.227f1cd8.jhnikula@gmail.com> (raw)
In-Reply-To: <20100106145321.GC5783@sirena.org.uk>
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
next prev parent reply other threads:[~2010-01-06 15:48 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-05 2:10 question on dapm_reg_event() Haojian Zhuang
2010-01-06 14:53 ` Mark Brown
2010-01-06 15:48 ` Jarkko Nikula [this message]
2010-01-06 15:59 ` Mark Brown
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