toshiba_acpi: Refuse to load on machines with buggy INFO implementations

Several Satellite models have a buggy implementation of the INFO method
that causes ACPI exceptions when executed:

 ACPI Error: Result stack is empty! State=ffff88012d70f800 (20110413/dswstate-98)
 ACPI Exception: AE_AML_NO_RETURN_VALUE, Missing or null operand (20110413/dsutils-646)
 ACPI Exception: AE_AML_NO_RETURN_VALUE, While creating Arg 0 (20110413/dsutils-763)
 ACPI Error: Method parse/execution failed [\_SB_.VALZ.GETE] (Node ffff880131175eb0), AE_AML_NO_RETURN_VALUE (20110413/psparse-536)
 ACPI Error: Method parse/execution failed [\_SB_.VALZ.INFO] (Node ffff880131175ed8), AE_AML_NO_RETURN_VALUE (20110413/psparse-536)
 toshiba_acpi: ACPI INFO method execution failed
 toshiba_acpi: Failed to query hotkey event

All known machines with this implementation also have a WMI interface
with event GUID 59142400-C6A3-40FA-BADB-8A2652834100 which is not seen
on any other models. Refuse to load toshiba_acpi on machines with this
guid.
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/Kconfig

@@ -569,6 +569,7 @@ config TOPSTAR_LAPTOP
 config ACPI_TOSHIBA
 	tristate "Toshiba Laptop Extras"
 	depends on ACPI
+	depends on ACPI_WMI
 	select LEDS_CLASS
 	select NEW_LEDS
 	depends on BACKLIGHT_CLASS_DEVICE

drivers/platform/x86/Makefile

@@ -30,7 +30,11 @@ obj-$(CONFIG_INTEL_MENLOW)	+= intel_menlow.o
 obj-$(CONFIG_ACPI_WMI)		+= wmi.o
 obj-$(CONFIG_MSI_WMI)		+= msi-wmi.o
 obj-$(CONFIG_TOPSTAR_LAPTOP)	+= topstar-laptop.o
+
+# toshiba_acpi must link after wmi to ensure that wmi devices are found
+# before toshiba_acpi initializes
 obj-$(CONFIG_ACPI_TOSHIBA)	+= toshiba_acpi.o
+
 obj-$(CONFIG_TOSHIBA_BT_RFKILL)	+= toshiba_bluetooth.o
 obj-$(CONFIG_INTEL_SCU_IPC)	+= intel_scu_ipc.o
 obj-$(CONFIG_INTEL_SCU_IPC_UTIL) += intel_scu_ipcutil.o

drivers/platform/x86/toshiba_acpi.c

@@ -63,6 +63,8 @@ MODULE_AUTHOR("John Belmonte");
 MODULE_DESCRIPTION("Toshiba Laptop ACPI Extras Driver");
 MODULE_LICENSE("GPL");
 
+#define TOSHIBA_WMI_EVENT_GUID "59142400-C6A3-40FA-BADB-8A2652834100"
+
 /* Scan code for Fn key on TOS1900 models */
 #define TOS1900_FN_SCAN		0x6e
 
@@ -1249,6 +1251,14 @@ static int __init toshiba_acpi_init(void)
 {
 	int ret;
 
+	/*
+	 * Machines with this WMI guid aren't supported due to bugs in
+	 * their AML. This check relies on wmi initializing before
+	 * toshiba_acpi to guarantee guids have been identified.
+	 */
+	if (wmi_has_guid(TOSHIBA_WMI_EVENT_GUID))
+		return -ENODEV;
+
 	toshiba_proc_dir = proc_mkdir(PROC_TOSHIBA, acpi_root_dir);
 	if (!toshiba_proc_dir) {
 		pr_err("Unable to create proc dir " PROC_TOSHIBA "\n");