linux-kernel - Re: [PATCH] s3c/s3c24xx: arm: leds: Make s3c24xx LEDS driver use gpiolib

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Date:	Tue, 22 Nov 2011 02:28:22 +0200
From:	Denis Kuzmenko <linux@...onet.org.ua>
To:	Stephen Warren <swarren@...dia.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...aro.org>,
	Richard Purdie <rpurdie@...ys.net>,
	Wolfram Sang <w.sang@...gutronix.de>
Subject: Re: [PATCH] s3c/s3c24xx: arm: leds: Make s3c24xx LEDS driver use
 gpiolib

On 11/22/2011 01:39 AM, Stephen Warren wrote:
> Denis Kuzmenko wrote at Monday, November 21, 2011 3:52 PM:
> ...
>>> I don't see any pulls being configured in the original code at all,
>>> unless some of the s3c2410_* function have unexpected side-effect. The
>>> only related thing is in probe:
>>>
>>>         /* no point in having a pull-up if we are always driving */
>>>
>>>         if (pdata->flags & S3C24XX_LEDF_TRISTATE) {
>>> ..
>>>         } else {
>>>                 s3c2410_gpio_pullup(pdata->gpio, 0);
>>>
>>> which I assume disables an pull in the case where the pin is always driven.
>>>
>>> So, yes, I'd say submit v3 without any pull manipulation at all.
>>>
>>
>> Actually, "s3c2410_gpio_pullup(pdata->gpio, 0);" enables pull in the
>> same way I've done that. Here is it's code:
> 
> So it does. That's extremely non-obvious if not broken.
> 
> Anyway, I guess that means that your patch V1 is at least a pure conversion
> of the code from custom functions to gpiolib, even if what it was and still
> is doing doesn't make much sense to me.
> 

So what do you suggest? Leave original behavior?
I'd like to remove pull-related actions at all considering:
 - power consumption
 - we are both not able to find any sense in that code
 - s3c2410_gpio_pullup looks like deprecated
 - can't imagine situation where this change will break functionality
(of course when this code used to drive actually LED and not something else)

-- 
Best regards, Denis Kuzmenko.
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