ACPI: blacklist win8 OSI for ASUS Zenbook Prime UX31A

Since v3.7 the ACPI backlight driver doesn't work at all on this
machine, because presumably the backlight AML code in the ACPI
tables contains a code path that triggers when the OS identifies
itself as compatible with Windows 8 (which the kernel started to
do in 3.7).  That code path is never used by Windows and on this
particular machine it turns out to be unusable at all.

Work around this problem by blacklisting the win8 OSI, so we are back
to v3.6 behavior (that is, we don't tell the BIOS that we are
compatible with Windows 8).

Since v3.7, users have been forced to work around the initial
regression by modifying the boot arguments [1].

[1] https://wiki.archlinux.org/index.php/ASUS_Zenbook_Prime_UX31A

[rjw: Changelog]
Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/blacklist.c b/drivers/acpi/blacklist.c
index cb9629638def78fdd1432dc06102c2a5f5097a24..a404127768045f5b2fb1fe7a6035cf5ec2a0f93a 100644 (file)
--- a/drivers/acpi/blacklist.c
+++ b/drivers/acpi/blacklist.c
@@ -192,6 +192,12 @@ static int __init dmi_disable_osi_win7(const struct dmi_system_id *d)
        acpi_osi_setup("!Windows 2009");
        return 0;
 }
+static int __init dmi_disable_osi_win8(const struct dmi_system_id *d)
+{
+       printk(KERN_NOTICE PREFIX "DMI detected: %s\n", d->ident);
+       acpi_osi_setup("!Windows 2012");
+       return 0;
+}
 
 static struct dmi_system_id acpi_osi_dmi_table[] __initdata = {
        {
@@ -267,6 +273,14 @@ static struct dmi_system_id acpi_osi_dmi_table[] __initdata = {
                     DMI_MATCH(DMI_PRODUCT_NAME, "Satellite P305D"),
                },
        },
+       {
+       .callback = dmi_disable_osi_win8,
+       .ident = "ASUS Zenbook Prime UX31A",
+       .matches = {
+                    DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+                    DMI_MATCH(DMI_PRODUCT_NAME, "UX31A"),
+               },
+       },
 
        /*
         * BIOS invocation of _OSI(Linux) is almost always a BIOS bug.