1 files changed, 28 insertions, 15 deletions

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 2ea1781290cc..0c884020f74b 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -1392,7 +1392,7 @@ acpi_video_get_next_level(struct acpi_video_device *device,
 				break;
 		}
 	}
-	/* Ajust level_current to closest available level */
+	/* Adjust level_current to closest available level */
 	level_current += delta;
 	for (i = ACPI_VIDEO_FIRST_LEVEL; i < device->brightness->count; i++) {
 		l = device->brightness->levels[i];
@@ -1555,7 +1555,7 @@ acpi_video_bus_get_devices(struct acpi_video_bus *video,
 
 /*
  * Win8 requires setting bit2 of _DOS to let firmware know it shouldn't
- * preform any automatic brightness change on receiving a notification.
+ * perform any automatic brightness change on receiving a notification.
  */
 static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
 {
@@ -2182,6 +2182,30 @@ static bool dmi_is_desktop(void)
 	return false;
 }
 
+/*
+ * We're seeing a lot of bogus backlight interfaces on newer machines
+ * without a LCD such as desktops, servers and HDMI sticks. Checking the
+ * lcd flag fixes this, enable this by default on any machines which are:
+ * 1.  Win8 ready (where we also prefer the native backlight driver, so
+ *     normally the acpi_video code should not register there anyways); *and*
+ * 2.1 Report a desktop/server DMI chassis-type, or
+ * 2.2 Are an ACPI-reduced-hardware platform (and thus won't use the EC for
+       backlight control)
+ */
+static bool should_check_lcd_flag(void)
+{
+	if (!acpi_osi_is_win8())
+		return false;
+
+	if (dmi_is_desktop())
+		return true;
+
+	if (acpi_reduced_hardware())
+		return true;
+
+	return false;
+}
+
 int acpi_video_register(void)
 {
 	int ret = 0;
@@ -2195,19 +2219,8 @@ int acpi_video_register(void)
 		goto leave;
 	}
 
-	/*
-	 * We're seeing a lot of bogus backlight interfaces on newer machines
-	 * without a LCD such as desktops, servers and HDMI sticks. Checking
-	 * the lcd flag fixes this, so enable this on any machines which are
-	 * win8 ready (where we also prefer the native backlight driver, so
-	 * normally the acpi_video code should not register there anyways).
-	 */
-	if (only_lcd == -1) {
-		if (dmi_is_desktop() && acpi_osi_is_win8())
-			only_lcd = true;
-		else
-			only_lcd = false;
-	}
+	if (only_lcd == -1)
+		only_lcd = should_check_lcd_flag();
 
 	dmi_check_system(video_dmi_table);