Re: [PATCH] Platform: Brightness quirk for samsung laptop driver

[Greg KH <greg@kroah.com>]

On Fri, Aug 26, 2011 at 01:31:38PM +0200, David Herrmann wrote:
> On Fri, Aug 26, 2011 at 11:58 AM, Jason Stubbs <jasonbstubbs@gmail.com> wrote:
> > From: Jason Stubbs <jasonbstubbs@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@gmail.com>
> >
> > ---
> >
> > diff --git a/drivers/platform/x86/samsung-laptop.c b/drivers/platform/x86/samsung-laptop.c
> > index ee68c1c..b193bf0 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);
> > @@ -796,6 +836,9 @@ 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))
> >
> >
> 
> Thank you, Jason.
> Tested-by: David Herrmann <dh.herrmann@googlemail.com>
> 
> And Greg, could you actually "git add" the new samsung patches in your
> repository? You added them to "series" but didn't submit the actual
> patch files. That would be great.

Now done, sorry about that.

greg k-h