[PATCH] platform: samsung_laptop: fix samsung brightness min/max calculations

[Jason Stubbs <jasonbstubbs@gmail.com>]

From: Jason Stubbs <jasonbstubbs@gmail.com>

The min_brightness value of the sabi_config is incorrectly used in brightness
calculations. For the config where min_brightness = 1 and max_brightness = 8,
the user visible range should be 0 to 7 with hardware being set in the range
of 1 to 8. What is actually happening is that the user visible range is 0 to
8 with hardware being set in the range of -1 to 7.

This patch fixes the above issue as well as a miscalculation that would occur
in the case of min_brightness > 1.

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 4c78dbc..aad14ab 100644
--- a/drivers/platform/x86/samsung-laptop.c
+++ b/drivers/platform/x86/samsung-laptop.c
@@ -371,15 +371,17 @@ 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;
 
 	if (has_stepping_quirk && user_level != 0) {
 		/*
@@ -834,7 +836,8 @@ 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);