linux-kernel - Re: [PATCH v5 07/23] regulator: core: Remove regulator

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Date:	Mon, 21 Sep 2015 16:08:33 +0200
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Mark Brown <broonie@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-acpi@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	Stephen Warren <swarren@...dotorg.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 07/23] regulator: core: Remove regulator_list

On 20 September 2015 at 22:32, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Sat, Sep 19, 2015 at 08:01:29AM -0700, Mark Brown wrote:
>> On Thu, Sep 17, 2015 at 02:57:01PM +0200, Tomeu Vizoso wrote:
>> > As we are already registering a device with regulator_class for each
>> > regulator device, regulator_list is redundant and can be replaced with
>> > calls to class_find_device() and class_for_each_device().
>>
>> This appears to leak references to the struct devices returned by
>> class_find_device() - it takes a reference before it returns so any
>> device found using class_find_device() needs to be released with
>> put_device() and I don't see any new put_device() calls in here.
>
> When I've been fiding exactly that kind of bug in the PHY code, I've
> been adding comments to the docbook function header detailing the
> requirement to balance the reference.  IMHO, this is a good idea,
> because the more places that get it with these APIs, the more likely
> people are to potentially read it.
>
> The comment I've been putting in the phy code is:
>
>  * If successful, returns a pointer to the phy_device with the embedded
>  * struct device refcount incremented by one, or NULL on failure. The
>  * refcount must be dropped by calling phy_disconnect() or phy_detach().
>
> which even goes as far as telling people how they should be dropping
> the reference.  So there should be no excuse (ignorance is not an
> excuse for this!)

Thanks for the suggestion, I have gone with it.

Regards,

Tomeu

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