ACPI: EC: Add some basic check for ECDT data

One more ASUS comes with empty ECDT, add a guard for it...

http://bugzilla.kernel.org/show_bug.cgi?id=11880Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/ec.c

@@ -977,7 +977,6 @@ static const struct acpi_device_id ec_device_ids[] = {
 
 int __init acpi_ec_ecdt_probe(void)
 {
-	int ret;
 	acpi_status status;
 	struct acpi_table_ecdt *ecdt_ptr;
 
@@ -1005,7 +1004,11 @@ int __init acpi_ec_ecdt_probe(void)
 		boot_ec->gpe = ecdt_ptr->gpe;
 		boot_ec->handle = ACPI_ROOT_OBJECT;
 		acpi_get_handle(ACPI_ROOT_OBJECT, ecdt_ptr->id, &boot_ec->handle);
-	} else {
+		/* Add some basic check against completely broken table */
+		if (boot_ec->data_addr != boot_ec->command_addr)
+			goto install;
+	/* fall through */
+	}
 	/* This workaround is needed only on some broken machines,
 	 * which require early EC, but fail to provide ECDT */
 	acpi_handle x;
@@ -1021,14 +1024,12 @@ int __init acpi_ec_ecdt_probe(void)
 	 */
 	if (ACPI_FAILURE(acpi_get_handle(boot_ec->handle, "_INI", &x)))
 		return -ENODEV;
-	}
-
-	ret = ec_install_handlers(boot_ec);
-	if (!ret) {
+install:
+	if (!ec_install_handlers(boot_ec)) {
 		first_ec = boot_ec;
 		return 0;
 	}
-      error:
+error:
 	kfree(boot_ec);
 	boot_ec = NULL;
 	return -ENODEV;