platform/x86: surfacepro3_button: Fix device check

Do not use the surfacepro3_button driver on newer Microsoft Surface
models, only use it on the Surface Pro 3 and 4. Newer models (5th, 6th
and possibly future generations) use the same device as the Surface Pro
4 to represent their volume and power buttons (MSHW0040), but their
actual implementation is significantly different. This patch ensures
that the surfacepro3_button driver is only used on the Pro 3 and 4
models, allowing a different driver to bind on other models.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/platform/x86/surfacepro3_button.c b/drivers/platform/x86/surfacepro3_button.c
index 47c6d000465a..ec515223f654 100644
--- a/drivers/platform/x86/surfacepro3_button.c
+++ b/drivers/platform/x86/surfacepro3_button.c
@@ -20,6 +20,12 @@
 #define SURFACE_BUTTON_OBJ_NAME         "VGBI"
 #define SURFACE_BUTTON_DEVICE_NAME      "Surface Pro 3/4 Buttons"
 
+#define MSHW0040_DSM_REVISION           0x01
+#define MSHW0040_DSM_GET_OMPR           0x02    // get OEM Platform Revision
+static const guid_t MSHW0040_DSM_UUID =
+        GUID_INIT(0x6fd05c69, 0xcde3, 0x49f4, 0x95, 0xed, 0xab, 0x16, 0x65,
+                  0x49, 0x80, 0x35);
+
 #define SURFACE_BUTTON_NOTIFY_TABLET_MODE       0xc8
 
 #define SURFACE_BUTTON_NOTIFY_PRESS_POWER       0xc6
@@ -142,6 +148,44 @@ static int surface_button_resume(struct device *dev)
 }
 #endif
 
+/*
+ * Surface Pro 4 and Surface Book 2 / Surface Pro 2017 use the same device
+ * ID (MSHW0040) for the power/volume buttons. Make sure this is the right
+ * device by checking for the _DSM method and OEM Platform Revision.
+ *
+ * Returns true if the driver should bind to this device, i.e. the device is
+ * either MSWH0028 (Pro 3) or MSHW0040 on a Pro 4 or Book 1.
+ */
+static bool surface_button_check_MSHW0040(struct acpi_device *dev)
+{
+        acpi_handle handle = dev->handle;
+        union acpi_object *result;
+        u64 oem_platform_rev = 0;       // valid revisions are nonzero
+
+        // get OEM platform revision
+        result = acpi_evaluate_dsm_typed(handle, &MSHW0040_DSM_UUID,
+                                         MSHW0040_DSM_REVISION,
+                                         MSHW0040_DSM_GET_OMPR,
+                                         NULL, ACPI_TYPE_INTEGER);
+
+        /*
+         * If evaluating the _DSM fails, the method is not present. This means
+         * that we have either MSHW0028 or MSHW0040 on Pro 4 or Book 1, so we
+         * should use this driver. We use revision 0 indicating it is
+         * unavailable.
+         */
+
+        if (result) {
+                oem_platform_rev = result->integer.value;
+                ACPI_FREE(result);
+        }
+
+        dev_dbg(&dev->dev, "OEM Platform Revision %llu\n", oem_platform_rev);
+
+        return oem_platform_rev == 0;
+}
+
+
 static int surface_button_add(struct acpi_device *device)
 {
         struct surface_button *button;
@@ -154,6 +198,9 @@ static int surface_button_add(struct acpi_device *device)
             strlen(SURFACE_BUTTON_OBJ_NAME)))
                 return -ENODEV;
 
+        if (!surface_button_check_MSHW0040(device))
+                return -ENODEV;
+
         button = kzalloc(sizeof(struct surface_button), GFP_KERNEL);
         if (!button)
                 return -ENOMEM;