Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit ac080523 authored by Jason Stubbs's avatar Jason Stubbs Committed by Matthew Garrett
Browse files

Platform: Brightness quirk for samsung laptop driver 



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: default avatarJason Stubbs <jasonbstubbs@gmail.com>
Tested-by: default avatarDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: default avatarMatthew Garrett <mjg@redhat.com>
parent a7ea1992

drivers/platform/x86/samsung-laptop.c

+43 −0
Original line number Diff line number Diff line
@@ -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);
@@ -805,6 +845,9 @@ 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))