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

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Date:	Sat, 14 Mar 2009 21:27:26 -0700
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 Saturday 14 March 2009, Mark Brown wrote:
> Looking at things from the point of view of the consumer I just don't
> find that it makes any difference since as far as the consumer is
> concerned it's all opaque objects manipulated via an API.

These put()/get() calls are not refcount calls.  They're
what might be called alloc()/free() calls instead.

>         foo = foo_get(dev, name);

The normal idiom is

	bar = foo_get(foo)

which just increments a refcount.  Then if "bar" were handed
to something else ("baz") right here, and "baz" needed to keep a
copy of that reference, it would be expected to grab its own
refcount via foo_get(bar), and later release via foo_put(bar).


>         foo_enable(foo);
>         foo_disable(foo);
>         foo_put(foo);

Until "baz" called foo_put(bar), that reference would still be
usable.  But ... regulator_put(foo) does a kfree, it's not
just updating refcounts.
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