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

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Date:	Thu, 5 Jul 2012 17:12:28 +0900
From:	Alex Courbot <acourbot@...dia.com>
To:	Thierry Reding <thierry.reding@...onic-design.de>
CC:	Sascha Hauer <s.hauer@...gutronix.de>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	"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 07/05/2012 04:57 PM, Thierry Reding wrote:
> I agree. Non-DT platforms have always used the callbacks to execute this
> kind of code. As you've said before there are situations where it isn't
> just about setting a GPIO or enabling a regulator but it also requires a
> specific timing. Representing this in the platform data would become
> tedious.

That will settle the whole issue then.

> So I think for the DT case you can parse the power-on and power-off
> sequences directly and execute code based on it, while in non-DT cases
> the init and exit callbacks should be used instead. I think it even
> makes sense to reuse the platform data's init and exit functions in the
> DT case and implement the parser/interpreter within those.

It totally makes sense indeed.

> I case where the regulator comes from a DT it should assume that it will
> become available at some point, so -EPROBE_DEFER is correct. However if
> the DT doesn't even contain the power-supply property, then EPROBE_DEFER
> will never work because there's no regulator to become available.

Indeed. And as Sascha mentionned this could easily be fixed. Guess I can 
also submit a patch for that while I am at it.

Alex.
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