linux-kernel - Re: [patch 2.6.29-rc7 regulator-next] regulator: refcount fixes

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Message-Id: <200903121335.25368.david-b@pacbell.net>
Date:	Thu, 12 Mar 2009 12:35:24 -0800
From:	David Brownell <david-b@...bell.net>
To:	Mark Brown <broonie@...ena.org.uk>
Cc:	Liam Girdwood <lrg@...mlogic.co.uk>,
	lkml <linux-kernel@...r.kernel.org>,
	OMAP <linux-omap@...r.kernel.org>
Subject: Re: [patch 2.6.29-rc7 regulator-next] regulator: refcount fixes

On Thursday 12 March 2009, Mark Brown wrote:
> On Wed, Mar 11, 2009 at 04:43:34PM -0800, David Brownell wrote:
> 
> > Buggy consumers could notice different bug symptoms.  The main
> > example would be refcounting bugs; also, any (out-of-tree) users
> > of the experimental regulator_set_optimum_mode() stuff which
> > don't call it when they're done using a regulator.
> 
> I'm OK with this from a code point of view so
> 
> Acked-by: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> 
> However any consumers that take advantage of this won't be able to
> safely share a regulator without extra work since they have no way of
> telling why a regulator is in the state that it's in without extra
> stuff.

Depends what you mean by "safely".  If they weren't buggy
already, I don't see how they'd notice any difference.
Having buggy consumers become non-buggy isn't exactly a
job for the framework itself.


> We should probably have something along the lines of a 
> regulator_get_exclusive() for them.  Previously the consumer counting
> would have stopped them interfering with enables done by other
> consumers.

I'd like to see get()/put() match the design pattern used
elsewhere in the kernel:  those calls signify refcount
operations.

Agreed that the "consumer" access model probably needs a few
interface updates.  I'm not sure what they would be though;
one notion would be to focus on the constraints they apply
(including "enabled") instead of what they do now.

 
> There will be other consumers that can't safely share a regulator anyway
> (eg, requiring additional code to notice and handle voltage changes) so
> it'd be a good thing to have.


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