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

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Date:	Thu, 5 Jul 2012 00:14:39 +0900
From:	Alex Courbot <acourbot@...dia.com>
To:	Sascha Hauer <s.hauer@...gutronix.de>
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 04 Jul 2012 10:00:56 PM JST, Sascha Hauer wrote:
>> 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.

As far as I can tell the gpio is allocated through devm as well:

 > +		ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 > +				GPIOF_OUT_INIT_HIGH, "backlight_enable");

Thus if it is not reclaimed with probe returns with -EPROBE_DEFER, then 
I guess something is going wrong elsewhere. You are right that the PWM 
should be freed by the driver thought.

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

Sorry, I don't see why. Could you elaborate on this?

Thanks,
Alex.

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