ACPI: ibm-acpi: improve backlight power handling

Improve the backlight code to emulate as much as possible the power
management events, as we are unable to really power on or power off the
backlight.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Acked-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/ibm_acpi.c

@@ -86,6 +86,7 @@
 
 #include <linux/proc_fs.h>
 #include <linux/backlight.h>
+#include <linux/fb.h>
 #include <asm/uaccess.h>
 
 #include <linux/dmi.h>
@@ -1707,7 +1708,10 @@ static int brightness_write(char *buf)
 
 static int brightness_update_status(struct backlight_device *bd)
 {
-	return brightness_set(bd->props.brightness);
+	return brightness_set(
+		(bd->props.fb_blank == FB_BLANK_UNBLANK &&
+		 bd->props.power == FB_BLANK_UNBLANK) ?
+				bd->props.brightness : 0);
 }
 
 static struct backlight_ops ibm_backlight_data = {