[PATCH] powermac backlight fixes

Fix a erroneous calculation of the legacy brightness values as reported by
Paul Collins.  Additionally, it moves the calculation of the negative value
in the radeonfb driver after the value check.
Signed-off-by: NMichael Hanselmann <linux-kernel@hansmi.ch>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: NPaul Collins <paul@briny.ondioline.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/powerpc/platforms/powermac/backlight.c

@@ -119,7 +119,14 @@ int pmac_backlight_set_legacy_brightness(int brightness)
 		down(&pmac_backlight->sem);
 		props = pmac_backlight->props;
 		props->brightness = brightness *
-			props->max_brightness / OLD_BACKLIGHT_MAX;
+			(props->max_brightness + 1) /
+			(OLD_BACKLIGHT_MAX + 1);
+
+		if (props->brightness > props->max_brightness)
+			props->brightness = props->max_brightness;
+		else if (props->brightness < 0)
+			props->brightness = 0;
+
 		props->update_status(pmac_backlight);
 		up(&pmac_backlight->sem);
 
@@ -140,8 +147,11 @@ int pmac_backlight_get_legacy_brightness()
 
 		down(&pmac_backlight->sem);
 		props = pmac_backlight->props;
+
 		result = props->brightness *
-			OLD_BACKLIGHT_MAX / props->max_brightness;
+			(OLD_BACKLIGHT_MAX + 1) /
+			(props->max_brightness + 1);
+
 		up(&pmac_backlight->sem);
 	}
 	mutex_unlock(&pmac_backlight_mutex);

drivers/video/aty/radeon_backlight.c

@@ -40,14 +40,14 @@ static int radeon_bl_get_level_brightness(struct radeon_bl_privdata *pdata,
 
 	mutex_unlock(&info->bl_mutex);
 
-	if (pdata->negative)
-		rlevel = MAX_RADEON_LEVEL - rlevel;
-
 	if (rlevel < 0)
 		rlevel = 0;
 	else if (rlevel > MAX_RADEON_LEVEL)
 		rlevel = MAX_RADEON_LEVEL;
 
+	if (pdata->negative)
+		rlevel = MAX_RADEON_LEVEL - rlevel;
+
 	return rlevel;
 }