Ack: Re: [PATCH 1/1][Oneiric SRU] Platform: Brightness quirk for samsung laptop driver

[Herton Ronaldo Krzesinski]

On Fri, Dec 02, 2011 at 02:29:28PM -0600, Seth Forshee wrote:
> From: Jason Stubbs <jasonbstubbs at gmail.com>
> 
> On some Samsung laptops the brightness regulation works slightly different.
> All SABI commands except for set_brightness work as expected. The behaviour
> of set_brightness is as follows:
> 
> - Setting a new brightness will only step one level toward the new brightness
>   level. For example, setting a level of 5 when the current level is 2 will
>   result in a brightness level of 3.
> - A spurious KEY_BRIGHTNESS_UP or KEY_BRIGHTNESS_DOWN event is also generated
>   along with the change in brightness.
> - Neither of the above two issues occur when changing from/to brightness
>   level 0.
> 
> This patch adds detection and a non-intrusive workaround for the above issues.
> 
> Signed-off-by: Jason Stubbs <jasonbstubbs at gmail.com>
> Tested-by: David Herrmann <dh.herrmann at googlemail.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>
> Signed-off-by: Matthew Garrett <mjg at redhat.com>
> 
> (cherry picked from commit ac080523141d5bfa5f60ef2436480f645f915e9c)
> BugLink: http://bugs.launchpad.net/bugs/897378
> Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
> ---
>  drivers/platform/x86/samsung-laptop.c |   43 +++++++++++++++++++++++++++++++++
>  1 files changed, 43 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/platform/x86/samsung-laptop.c b/drivers/platform/x86/samsung-laptop.c
> index ec85987..c32dc39 100644
> --- a/drivers/platform/x86/samsung-laptop.c
> +++ b/drivers/platform/x86/samsung-laptop.c
> @@ -226,6 +226,7 @@ static struct backlight_device *backlight_device;
>  static struct mutex sabi_mutex;
>  static struct platform_device *sdev;
>  static struct rfkill *rfk;
> +static bool has_stepping_quirk;
>  
>  static int force;
>  module_param(force, bool, 0);
> @@ -382,6 +383,17 @@ static void set_brightness(u8 user_brightness)
>  {
>  	u8 user_level = user_brightness + sabi_config->min_brightness;
>  
> +	if (has_stepping_quirk && user_level != 0) {
> +		/*
> +		 * short circuit if the specified level is what's already set
> +		 * to prevent the screen from flickering needlessly
> +		 */
> +		if (user_brightness == read_brightness())
> +			return;
> +
> +		sabi_set_command(sabi_config->commands.set_brightness, 0);
> +	}
> +
>  	sabi_set_command(sabi_config->commands.set_brightness, user_level);
>  }
>  
> @@ -390,6 +402,34 @@ static int get_brightness(struct backlight_device *bd)
>  	return (int)read_brightness();
>  }
>  
> +static void check_for_stepping_quirk(void)
> +{
> +	u8 initial_level = read_brightness();
> +	u8 check_level;
> +
> +	/*
> +	 * Some laptops exhibit the strange behaviour of stepping toward
> +	 * (rather than setting) the brightness except when changing to/from
> +	 * brightness level 0. This behaviour is checked for here and worked
> +	 * around in set_brightness.
> +	 */
> +
> +	if (initial_level <= 2)
> +		check_level = initial_level + 2;
> +	else
> +		check_level = initial_level - 2;
> +
> +	has_stepping_quirk = false;
> +	set_brightness(check_level);
> +
> +	if (read_brightness() != check_level) {
> +		has_stepping_quirk = true;
> +		pr_info("enabled workaround for brightness stepping quirk\n");
> +	}
> +
> +	set_brightness(initial_level);
> +}
> +
>  static int update_status(struct backlight_device *bd)
>  {
>  	set_brightness(bd->props.brightness);
> @@ -813,6 +853,9 @@ static int __init samsung_init(void)
>  		}
>  	}
>  
> +	/* Check for stepping quirk */
> +	check_for_stepping_quirk();
> +
>  	/* knock up a platform device to hang stuff off of */
>  	sdev = platform_device_register_simple("samsung", -1, NULL, 0);
>  	if (IS_ERR(sdev))
> -- 
> 1.7.5.4
> 
> 
> -- 
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