make value 0 actually show something.

samsung-backlight.c

@@ -26,10 +26,14 @@
  * the brightness control.  And since 256 different levels seems a bit
  * overkill, that's fine.  So let's map the 256 values to 8 different ones:
  *
- * userspace	0    1    2    3    4    5    6    7
- * hardware	0   36   72  108  144  180  216  252
+ * userspace	 0    1    2    3    4    5    6    7
+ * hardware	31   63   95  127  159  195  223  255
  *
- * or hardware = (userspace * 36) - 1 iff userspace != 0
+ * or hardware = ((userspace + 1) * 32)-1
+ *
+ * Note, we keep value 0 at a positive value, otherwise the screen goes
+ * blank because HAL likes to set the backlight to 0 at startup when there is
+ * no power plugged in.
  */
 
 
@@ -46,18 +50,15 @@ static u8 read_brightness(void)
 	u8 user_brightness = 0;
 
 	pci_read_config_byte(pci_device, offset, &kernel_brightness);
-	if (kernel_brightness != 0)
-		user_brightness = kernel_brightness / 36;
-
+	user_brightness = ((kernel_brightness + 1) / 32) - 1;
 	return user_brightness;
 }
 
 static void set_brightness(u8 user_brightness)
 {
 	u16 kernel_brightness = 0;
 
-	if (user_brightness != 0)
-		kernel_brightness = (user_brightness * 36) - 1;
+	kernel_brightness = ((user_brightness + 1) * 32) - 1;
 	pci_write_config_byte(pci_device, offset, (u8)kernel_brightness);
 }