linux-kernel - Re: [PATCH] pwm-backlight: add regulator and GPIO support

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Date:	Wed, 4 Jul 2012 15:00:56 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Alex Courbot <acourbot@...dia.com>
Cc:	Thierry Reding <thierry.reding@...onic-design.de>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>
Subject: Re: [PATCH] pwm-backlight: add regulator and GPIO support

On Wed, Jul 04, 2012 at 09:26:58PM +0900, Alex Courbot wrote:
> Hi Sascha,
> 
> On 07/04/2012 07:48 PM, Sascha Hauer wrote:>> +
> >> +	pb->power_reg = devm_regulator_get(&pdev->dev, "power");
> >> +	if (IS_ERR(pb->power_reg))
> >> +		return PTR_ERR(pb->power_reg);
> >
> > This looses several resources allocated earlier, like the enable gpio
> > and the pwm. This is really bad here since I have no regulator specified
> > and devm_regulator_get returns with -EPROBE_DEFER. Next time the core
> > tries to probe the driver the driver bails out because the gpio and the
> > pwm is already requested.
> 
> That's very bad indeed. I assumed that the kernel would free
> devm-allocated resources after probe returned -EPROBE_DEFER,

It indeed does free devm allocated resources, but neither the gpio nor
the pwm are devm allocated.

Also please be aware that using a regulator in the pwm backlight will
instantly break all existing users. That's hardly your fault though.

Sascha

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