linux-kernel - Re: [PATCH] atmel_lcdfb: fix negative check on unsigned

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Date:	Fri, 18 Apr 2008 22:34:13 -0400
From:	Haavard Skinnemoen <hskinnemoen@...el.com>
To:	Roel Kluin <12o3l@...cali.nl>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: [PATCH] atmel_lcdfb: fix negative check on unsigned

Cc'ing the atmel_lcdfb maintainer...

On Thu, 17 Apr 2008 06:31:28 +0200
Roel Kluin <12o3l@...cali.nl> wrote:

> No signed negative values will get noticed
> 
> Signed-off-by: Roel Kluin <12o3l@...cali.nl>
> ---
> diff --git a/drivers/video/atmel_lcdfb.c b/drivers/video/atmel_lcdfb.c
> index fc65c02..4b927da 100644
> --- a/drivers/video/atmel_lcdfb.c
> +++ b/drivers/video/atmel_lcdfb.c
> @@ -422,13 +422,13 @@ static int atmel_lcdfb_set_par(struct fb_info *info)
>  
>  	value = DIV_ROUND_UP(clk_value_khz, PICOS2KHZ(info->var.pixclock));
>  
> -	value = (value / 2) - 1;
> -	dev_dbg(info->device, "  * programming CLKVAL = 0x%08lx\n", value);
> -
> -	if (value <= 0) {
> +	if ((value / 2) <= 1) {
> +		dev_dbg(info->device, "  * programming CLKVAL = 0x%08lx\n", (value/2)-1);

Makes sense...although I think there's another patch in the queue that
fixes this as well.

>  		dev_notice(info->device, "Bypassing pixel clock divider\n");
>  		lcdc_writel(sinfo, ATMEL_LCDC_LCDCON1, ATMEL_LCDC_BYPASS);
>  	} else {
> +		value = (value / 2) - 1;
> +		dev_dbg(info->device, "  * programming CLKVAL = 0x%08lx\n", value);
>  		lcdc_writel(sinfo, ATMEL_LCDC_LCDCON1, value << ATMEL_LCDC_CLKVAL_OFFSET);
>  		info->var.pixclock = KHZ2PICOS(clk_value_khz / (2 * (value + 1)));
>  		dev_dbg(info->device, "  updated pixclk:     %lu KHz\n",

Haavard
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