linux-kernel - Re: [PATCH] Platform: Detect samsung laptop quirk when initial level is zero

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Message-ID: <4E96C4A3.4070504@gmail.com>
Date:	Thu, 13 Oct 2011 21:59:47 +1100
From:	Jason Stubbs <jasonbstubbs@...il.com>
To:	John Serock <john.serock@...il.com>
CC:	gregkh@...e.de, platform-driver-x86@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Platform: Detect samsung laptop quirk when initial level
 is zero

On 13/10/11 9:42 PM, John Serock wrote:
> From: John Serock <john.serock@...il.com>
> 
> This patch depends on the "Platform: Brightness quirk for samsung
> laptop driver" patch from Jason Stubbs. This patch adds a check for an
> initial brightness level of 0; if the level is 0, this patch changes
> the brightness level to 1 before the driver attempts to detect the
> brightness quirk.
> 
> The Samsung N150 netbook experiences the brightness quirk. Without
> Jason's patch, the only brightness levels available on the N150 are 0,
> 1, and 8. This patch ensures that, when the initial brightness level
> is 0, the samsang-laptop driver detects the brightness quirk on the
> N150, thereby making brightness levels 0 through 8 available.
> 
> Signed-off-by: John Serock <john.serock@...il.com>
> 
> ---
> diff -uprN a/drivers/platform/x86/samsung-laptop.c
> b/drivers/platform/x86/samsung-laptop.c
> --- a/drivers/platform/x86/samsung-laptop.c	2011-10-12 13:51:15.030779179 -0400
> +++ b/drivers/platform/x86/samsung-laptop.c	2011-10-12 13:51:32.746867045 -0400
> @@ -404,8 +404,9 @@ static int get_brightness(struct backlig
> 
>  static void check_for_stepping_quirk(void)
>  {
> -	u8 initial_level = read_brightness();
> +	u8 initial_level;
>  	u8 check_level;
> +	u8 orig_level = read_brightness();
> 
>  	/*
>  	 * Some laptops exhibit the strange behaviour of stepping toward
> @@ -414,6 +415,11 @@ static void check_for_stepping_quirk(voi
>  	 * around in set_brightness.
>  	 */
> 
> +	if (orig_level == 0)
> +		set_brightness(1);
> +
> +	initial_level = read_brightness();
> +
>  	if (initial_level <= 2)
>  		check_level = initial_level + 2;
>  	else
> @@ -427,7 +433,7 @@ static void check_for_stepping_quirk(voi
>  		pr_info("enabled workaround for brightness stepping quirk\n");
>  	}
> 
> -	set_brightness(initial_level);
> +	set_brightness(orig_level);
>  }
> 
>  static int update_status(struct backlight_device *bd)

Acked-by: Jason Stubbs <jasonbstubbs@...il.com>

Thanks!

Regards,
Jason Stubbs
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