diff -Naur a/src/gpm-brightness.c b/src/gpm-brightness.c
--- a/src/gpm-brightness.c	2008-09-04 12:05:15.000000000 +0200
+++ b/src/gpm-brightness.c	2009-04-24 21:11:31.489612633 +0200
@@ -81,6 +81,34 @@
 }
 
 /**
+ * gpm_brightness_get_guarded_up:
+ * @min: Minimum value (inclusive)
+ * @cur: Current value
+ * @max: Maximum value (inclusive)
+ * Return value: the minimum of (cur + step (min, max)) and max
+ **/
+guint
+gpm_brightness_get_guarded_up (guint min, guint cur, guint max)
+{
+	guint step = (max - min) / GPM_BRIGHTNESS_DIM_LEVELS;
+	return cur + step > max ? max : cur + step;
+}
+
+/**
+ * gpm_brightness_get_guarded_down:
+ * @min: Minimum value (inclusive)
+ * @cur: Current value
+ * @max: Maximum value (inclusive)
+ * Return value: the maximum of (cur - step (min, max)) and min
+ **/
+guint
+gpm_brightness_get_guarded_down (guint min, guint cur, guint max)
+{
+	guint step = (max - min) / GPM_BRIGHTNESS_DIM_LEVELS;
+	return min + step > cur ? min : cur - step;
+}
+
+/**
  * gpm_brightness_trust_cache:
  * @brightness: This brightness class instance
  * Return value: if we can trust the cache
diff -Naur a/src/gpm-brightness.h b/src/gpm-brightness.h
--- a/src/gpm-brightness.h	2008-09-04 12:05:15.000000000 +0200
+++ b/src/gpm-brightness.h	2009-04-24 21:11:40.432985322 +0200
@@ -34,6 +34,7 @@
 #define GPM_BRIGHTNESS_GET_CLASS(o)	(G_TYPE_INSTANCE_GET_CLASS ((o), GPM_TYPE_BRIGHTNESS, GpmBrightnessClass))
 
 #define GPM_BRIGHTNESS_DIM_INTERVAL	5 /* ms */
+#define GPM_BRIGHTNESS_DIM_LEVELS	12
 
 typedef struct GpmBrightnessPrivate GpmBrightnessPrivate;
 
@@ -66,6 +67,12 @@
 
 /* not designed to be used outside of gpm-brightness-*.c */
 guint		 gpm_brightness_get_step	(guint			 levels);
+guint		 gpm_brightness_get_guarded_up	(guint			 min,
+						 guint			 cur,
+						 guint			 max);
+guint		 gpm_brightness_get_guarded_down(guint			 min,
+						 guint			 cur,
+						 guint			 max);
 
 G_END_DECLS