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Old 12-02-2011, 08:03 PM
Herton Ronaldo Krzesinski
 
Default Ack: Platform: Brightness quirk for samsung laptop driver

On Fri, Dec 02, 2011 at 02:29:28PM -0600, Seth Forshee 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>
> Tested-by: David Herrmann <dh.herrmann@googlemail.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
> Signed-off-by: Matthew Garrett <mjg@redhat.com>
>
> (cherry picked from commit ac080523141d5bfa5f60ef2436480f645f915e9c)
> BugLink: http://bugs.launchpad.net/bugs/897378
> Signed-off-by: Seth Forshee <seth.forshee@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
");
> + }
> +
> + 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
>
>
> --
> kernel-team mailing list
> kernel-team@lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team
>

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