linux-kernel - Re: [PATCH 4/4] ASoC: TWL4030: Driver registration via twl4030

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Date:	Tue, 20 Oct 2009 12:51:06 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Peter Ujfalusi <peter.ujfalusi@...ia.com>
Cc:	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"sameo@...ux.intel.com" <sameo@...ux.intel.com>,
	"tony@...mide.com" <tony@...mide.com>
Subject: Re: [PATCH 4/4] ASoC: TWL4030: Driver registration via
 twl4030_codec MFD

On Tue, Oct 20, 2009 at 02:30:49PM +0300, Peter Ujfalusi wrote:

> In patch 1, the register definitions had to be added, so that the twl4030_codec 
> driver knows the registers (and there could be the vibra driver placed 
> separately from the soc codec driver).
> In patch 3, where I modify the soc codec driver to use the new method, than I 
> remove the definitions and use the existing header file, introduced by the first 
> patch.
> All in all, after each patch the kernel can be builds, boots and works as 
> before.

Sure, though I suspect patch 3 could just be split in two happily with
an include.  I don't really mind either way.  If you are going to keep
them as one patch it'd be good to call out the move in the changelog.

> > You've also got the bias being brought up when the ASoC system comes up
> > rather than when the driver comes up.  To be honest it doesn't really
> > make any difference either way, it's just slightly different to other
> > drivers.

> I was thinking that if you built the kernel with SND_SOC_ALL_CODECS on OMAP 
> platform for some reason and you don't actually use the twl4030 as audio device 
> -> no machine driver, which would use it, than the codec part would be off.
> But yes, probably I can move the povering up to the probe function.

That's a good enough reason to leave things as they are, though really
if you're building SND_SOC_ALL_CODECs in a production system you're
being a bit strange.

> > > +MODULE_ALIAS("platform:twl4030_codec:audio");

> > Is that second colon right given...

> I'm not sure about it at all either. I did not found any other 'nested MFD' 
> drivers around, so this is just a guess
> Should it be:

>  +MODULE_ALIAS("platform:twl4030_codec_audio");

Yes.  The aliasing makes no reference to the parents of the device, it
only cares about the device name - for the purposes of module loading
and driver matching it's identical to any other platform device.
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