linux-kernel - Re: [PATCH] regulator: core: Get and put regulator of

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Message-ID: <20140403105804.GP1665@opensource.wolfsonmicro.com>
Date:	Thu, 3 Apr 2014 11:58:04 +0100
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	lgirdwood@...il.com, linux-kernel@...r.kernel.org,
	patches@...nsource.wolfsonmicro.com
Subject: Re: [PATCH] regulator: core: Get and put regulator of_node

On Wed, Apr 02, 2014 at 05:53:54PM +0100, Mark Brown wrote:
> To make this correct we need to at least ensure that the node passed
> into the regulator API is valid and referenced at that time so there
> should only be an issue for the core if the reference is dropped after
> that.  In the above case the device model is holding a reference since
> this is the of_node for the device itself so taking the reference won't
> hurt but is redundant.  In cases where we have more than one regulator
> and are using of_regulator_match() then things are more tricky.
> Something needs to drop the references it returns (which isn't happening
> at all at the minute).

>From what I can see of_regulator_match isn't taking any
references at the minute? for_each_child_of_node will get a
reference but it will also put that when we process the next
child. We copy the pointer to the child into match->of_node
but don't manually increment the reference at all. So
of_regulator_match has no effect on the reference count of the
of_node.

>  Doing it while doing the match and register
> seems simple and neat from an error handling point of view so having the
> core take an additional reference during the registration would join up
> with that.

The main issue I have is that devm_regualtor_register is a bit
awkward. With regulator_register you will always be calling
regulator_unregister so you can put the of_node there but with
devm there isn't really a good place to put the of_node.

Would perhaps a sensible thing here be to add an of_node_get to
of_regulator_match, since we seem to be expecting that to
increase the ref count. And then just add an of_node_put to
regulator_unregister. And for anything directly using
regulator_register/devm_regulator_register they should add a
manual of_node_get?

Thanks,
Charles
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