linux-kernel - Re: [PATCH -mm 2/2] PWM LED driver

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Date:	Mon, 28 Jan 2008 01:29:32 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Haavard Skinnemoen <hskinnemoen@...el.com>
Cc:	David Brownell <david-b@...bell.net>,
	Andrew Victor <linux@...im.org.za>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Patrice Vilchez <patrice.vilchez@....atmel.com>,
	Richard Purdie <rpurdie@...ys.net>,
	linux-kernel@...r.kernel.org, kernel@...32linux.org,
	David Brownell <dbrownell@...rs.sourceforge.net>
Subject: Re: [PATCH -mm 2/2] PWM LED driver

On Mon, 28 Jan 2008 10:15:51 +0100 Haavard Skinnemoen <hskinnemoen@...el.com> wrote:

> On Sun, 27 Jan 2008 21:32:32 -0800
> Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> > On Thu, 24 Jan 2008 15:33:45 +0100 Haavard Skinnemoen <hskinnemoen@...el.com> wrote:
> > 
> > > +	if (i > 0) {
> > > +		for (i = i - 1; i >= 0; i--) {
> > > +			led_classdev_unregister(&leds[i].cdev);
> > > +			pwm_channel_free(&leds[i].pwmc);
> > > +		}
> > > +	}
> > 
> > Could be:
> > 
> > 	while (--i > 0) {
> > 		led_classdev_unregister(&leds[i].cdev);
> > 		pwm_channel_free(&leds[i].pwmc);
> > 	}
> > 
> > or thereabouts.
> 
> Almost...we need to clean up for leds[0] too. Using a postfix decrement
> should take care of that. How about the patch below?
> 
> Haavard
> 
> >From de5002ad71a1000f81817410f02a7d9fbd5d4ecd Mon Sep 17 00:00:00 2001
> From: Haavard Skinnemoen <hskinnemoen@...el.com>
> Date: Mon, 28 Jan 2008 10:14:14 +0100
> Subject: [PATCH] PWM led driver: Simplify cleanup loop
> 
> Why use a for loop inside an if() when we can get away with a simple
> while() loop?
> 
> Signed-off-by: Haavard Skinnemoen <hskinnemoen@...el.com>
> ---
>  drivers/leds/leds-atmel-pwm.c |    8 +++-----
>  1 files changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/leds/leds-atmel-pwm.c b/drivers/leds/leds-atmel-pwm.c
> index af61f55..187031c 100644
> --- a/drivers/leds/leds-atmel-pwm.c
> +++ b/drivers/leds/leds-atmel-pwm.c
> @@ -100,11 +100,9 @@ static int __init pwmled_probe(struct platform_device *pdev)
>  	return 0;
>  
>  err:
> -	if (i > 0) {
> -		for (i = i - 1; i >= 0; i--) {
> -			led_classdev_unregister(&leds[i].cdev);
> -			pwm_channel_free(&leds[i].pwmc);
> -		}
> +	while (i-- > 0) {
> +		led_classdev_unregister(&leds[i].cdev);
> +		pwm_channel_free(&leds[i].pwmc);
>  	}

Looks OK, although I'd say that `while (--i >= 0)' is more idiomatic -
predecrement, postincrement and all that?

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