linux-kernel - Re: [PATCH] regulator: Provide dummy supply support

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Message-ID: <20111102142931.GL23421@pengutronix.de>
Date:	Wed, 2 Nov 2011 15:29:31 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Mike Frysinger <vapier@...too.org>, linux-kernel@...r.kernel.org,
	Liam Girdwood <lrg@...com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Tony Lindgren <tony@...mide.com>, linux-sh@...r.kernel.org,
	linux-omap@...r.kernel.org, uclinux-dist-devel@...ckfin.uclinux.org
Subject: Re: [PATCH] regulator: Provide dummy supply support

On Wed, Nov 02, 2011 at 10:41:27AM +0000, Mark Brown wrote:
> On Wed, Nov 02, 2011 at 11:03:56AM +0100, Sascha Hauer wrote:
> > On Tue, Nov 01, 2011 at 06:27:21PM +0000, Mark Brown wrote:
> 
> > > As I think I said earlier I'd use the fixed regulator for this, all
> > > Sascha's actually doing here is adding a wrapper to simplify
> > > registration of that.
> 
> > There's one difference between the fixed and the dummy regulator though:
> > The fixed regulator has a voltage. The same dummy regulator instance can
> 
> No, the voltage is optional.

Ok, didn't know this.

> 
> > be used for all devices which do not have a software controllable
> > regulator. I think the same can be done with the fixed regulator aswell,
> > but the bogus voltage showing up in the sysfs entry might be confusing
> > to users.
> 
> I don't think that's a meaningful issue, any in any case it'd be better
> practice to fill it in so devices can use the information if they want
> to (which really shouldn't be hard
> 
> > Another approach to this topic would be to allow a board to explicitely
> > bind to the existing dummy regulator, like the following (error path
> > should of course be implemented before applying this)
> 
> If you know you've got a fixed voltage supply I don't understand why you
> wouldn't want to set one up.  There clearly is an actual supply in the
> system...

It's just that it's simpler for a board to provide all dummy supplies in
a single array, no matter if the real voltage is 1.8V or 3.3V. Anyway,
as the voltage is optional in a fixed regulator this is no problem. I'll
update my patch to use the fixed regulator then.

Sascha

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