mbp_nvidia_bl: check that the backlight control functions
The SMI-based backlight control functionality may fail to work if the
system is running under EFI rather than BIOS. Check that the hardware
responds as expected, and exit if it doesn't.
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Cc: Mourad De Clerck <mourad@aquazul.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/video/backlight/mbp_nvidia_bl.c b/drivers/video/backlight/mbp_nvidia_bl.c
index b22cfb2..dd0e145 100644
--- a/drivers/video/backlight/mbp_nvidia_bl.c
+++ b/drivers/video/backlight/mbp_nvidia_bl.c
@@ -143,6 +143,7 @@
{
struct backlight_properties props;
struct pci_dev *host;
+ int intensity;
host = pci_get_bus_and_slot(0, 0);
@@ -163,6 +164,18 @@
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;