linux-kernel - Re: [PATCH] pwm-backlight: add support for device tree gpio control

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Date:	Fri, 27 Sep 2013 09:55:51 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	Mike Dunn <mikedunn@...sguy.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Jingoo Han <jg1.han@...sung.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	<linux-pwm@...r.kernel.org>, <linux-fbdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Marek Vasut <marex@...x.de>
Subject: Re: [PATCH] pwm-backlight: add support for device tree gpio control

On 26/09/13 15:50, Thierry Reding wrote:

>> I thought the NAK was for the DT parts, not for the sequences as such. I
>> don't remember anyone shooting down the idea of defining power sequences
>> inside a driver.
> 
> Yes, but the DT parts were the primary reason why they were written in
> the first place. Without DT we can just use the existing hooks to do the
> sequencing. There is not much to be gained from power sequences.

Board hooks? Those cannot be used with DT boot.

But yes, the power sequences without DT (or platform data) parts cannot
handle with board-specific-things. I still think it'd be a very nice
thing to have inside the drivers. A single driver could more easily
handle bunch of somewhat similar devices, by specifying power sequences
in a table, one sequence for each device.

> There is unfortunately always the next crazy setup that one can think
> of. I personally prefer to support what we have (or at least the
> majority of that) with something generic and tackle the more exotic
> setups later on (or when they appear, as the case may be).
> 
> As things stand right now, there's no way to get the simplest panel
> setup to work properly if you use DT. By adding both an enable GPIO and
> a power supply regulator we can at least cover the sane use-cases with
> some sane and pretty simple code.

Sure, no disagreement there.

 Tomi



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