[PATCH 3/3] samsung-laptop: Disable on EFI hardware

[Brad Figg]

From: Matt Fleming <matt.fleming at intel.com>

BugLink: http://bugs.launchpad.net/bugs/1111689

It has been reported that running this driver on some Samsung laptops
with EFI can cause those machines to become bricked as detailed in the
following report,

	https://bugs.launchpad.net/ubuntu-cdimage/+bug/1040557

There have also been reports of this driver causing Machine Check
Exceptions on recent EFI-enabled Samsung laptops,

	https://bugzilla.kernel.org/show_bug.cgi?id=47121

So disable it if booting from EFI since this driver relies on
grovelling around in the BIOS memory map which isn't going to work.

Cc: Corentin Chary <corentincj at iksaif.net>
Cc: Matthew Garrett <mjg59 at srcf.ucam.org>
Cc: Colin Ian King <colin.king at canonical.com>
Cc: Steve Langasek <steve.langasek at canonical.com>
Cc: <stable at vger.kernel.org>
Signed-off-by: Matt Fleming <matt.fleming at intel.com>
Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>

Conflicts:

	drivers/platform/x86/samsung-laptop.c
Signed-off-by: Brad Figg <brad.figg at canonical.com>
(cherry picked from commit e0094244e41c4d0c7ad69920681972fc45d8ce34)
---
 drivers/platform/x86/samsung-laptop.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/platform/x86/samsung-laptop.c b/drivers/platform/x86/samsung-laptop.c
index e72ec12..5122698 100644
--- a/drivers/platform/x86/samsung-laptop.c
+++ b/drivers/platform/x86/samsung-laptop.c
@@ -26,6 +26,7 @@
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
 #include <linux/ctype.h>
+#include <linux/efi.h>
 #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
 #include <acpi/video.h>
 #endif
@@ -1537,6 +1538,9 @@ static int __init samsung_init(void)
 	struct samsung_laptop *samsung;
 	int ret;
 
+	if (efi_enabled(EFI_BOOT))
+		return -ENODEV;
+
 	quirks = &samsung_unknown;
 	if (!force && !dmi_check_system(samsung_dmi_table))
 		return -ENODEV;
-- 
1.7.9.5