From: Jason Stubbs <jasonbstubbs@xxxxxxxxx> 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: David Herrmann <dh.herrmann@xxxxxxxxxxxxxx> --- Hi This patch is originally from Jason Stubbs. See here: http://git.kernel.org/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=platform-samsung_laptop-add-support-for-samsung-nc210-nc110.patch;hb=HEAD I just wanted to ask whether there is some work going on here? My laptop model needs this fix and I reviewed and tested it and it works fine. It would be nice to see this upstream. I removed the NC210/NC120 device addition as it is not part of this change. This might be added in a separate patch. My laptop is detected as "N150P/N210P/N220P" and needs this quirk, too. I reviewed and tested it and it works fine. As it was signed-off earlier and released as GPL, I thought I'd just resubmit the patch. However, its not from me so a signed-off by Jason Stubbs would be nice again. Regards David 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 d347116..4cceb60 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); @@ -380,6 +381,17 @@ 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); } @@ -388,6 +400,34 @@ 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 (nc210/nc110 at the very least) 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); @@ -774,6 +814,9 @@ 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)) -- 1.7.6 -- To unsubscribe from this list: send the line "unsubscribe platform-driver-x86" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
