Re: [alsa-devel] question on dapm_reg_event()

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.