1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/video/backlight/mbp_nvidia_bl.c b/drivers/video/backlight/mbp_nvidia_bl.c
index b22cfb24bd55..dd0e145170b7 100644
--- a/drivers/video/backlight/mbp_nvidia_bl.c
+++ b/drivers/video/backlight/mbp_nvidia_bl.c
@@ -143,6 +143,7 @@ static int __devinit mb_bl_add(struct acpi_device *dev)
 {
         struct backlight_properties props;
         struct pci_dev *host;
+        int intensity;
 
         host = pci_get_bus_and_slot(0, 0);
 
@@ -163,6 +164,18 @@ static int __devinit mb_bl_add(struct acpi_device *dev)
                 return -ENODEV;
         }
 
+        /* Check that the hardware responds - this may not work under EFI */
+
+        intensity = hw_data->backlight_ops.get_brightness(NULL);
+
+        if (!intensity) {
+                hw_data->set_brightness(1);
+                if (!hw_data->backlight_ops.get_brightness(NULL))
+                        return -ENODEV;
+
+                hw_data->set_brightness(0);
+        }
+
         if (!request_region(hw_data->iostart, hw_data->iolen,
                             "Macbook backlight"))
                 return -ENXIO;