From: Jason Stubbs Subject: [PATCH] platform: fix samsung brightness min/max calculations For one of the SABI configs, the valid brightness levels are 1 through 8 with 0 being reserved for the BIOS. To make the range 0-based, the driver is meant to offset values to/from userspace by 1 giving valid levels of 0 through 7. Currently, the driver is reporting a max brightness of 8 and doing the offset the wrong way such that setting a brightness of 8 will set as 7 in hardware while setting a brightness of 0 will attempt (and fail) to set as -1 in hardware. This patch fixes these calculations as well as a potential miscalculation due to an assumption of min_brightness being either 0 or 1. Signed-off-by: Jason Stubbs Signed-off-by: Chuck Ebbert --- Originally posted here, context fixed to apply to 3.0/3.1: [ https://lkml.org/lkml/2011/5/11/548 ] diff a/drivers/platform/x86/samsung-laptop.c b/drivers/platform/x86/samsung-laptop.c --- a/drivers/platform/x86/samsung-laptop.c +++ b/drivers/platform/x86/samsung-laptop.c @@ -370,15 +370,17 @@ static u8 read_brightness(void) &sretval); if (!retval) { user_brightness = sretval.retval[0]; - if (user_brightness != 0) + if (user_brightness > sabi_config->min_brightness) user_brightness -= sabi_config->min_brightness; + else + user_brightness = 0; } return user_brightness; } static void set_brightness(u8 user_brightness) { - u8 user_level = user_brightness - sabi_config->min_brightness; + u8 user_level = user_brightness + sabi_config->min_brightness; sabi_set_command(sabi_config->commands.set_brightness, user_level); } @@ -802,7 +804,8 @@ static int __init samsung_init(void) /* create a backlight device to talk to this one */ memset(&props, 0, sizeof(struct backlight_properties)); props.type = BACKLIGHT_PLATFORM; - props.max_brightness = sabi_config->max_brightness; + props.max_brightness = sabi_config->max_brightness - + sabi_config->min_brightness; backlight_device = backlight_device_register("samsung", &sdev->dev, NULL, &backlight_ops, &props); _