On Tue, Jul 02, 2019 at 03:33:20AM +0200, Maximilian Luz wrote:

On 7/2/19 3:25 AM, Maximilian Luz wrote:

quoted

On 7/2/19 3:14 AM, Yu Chen wrote:

quoted

On Tue, Jul 02, 2019 at 02:37:39AM +0200, Maximilian Luz wrote:

quoted

+/*
+ * 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.
+ */
+static int surface_button_check_MSHW0040(struct acpi_device *dev)
+{
+    acpi_handle handle = dev->handle;
+    union acpi_object *result;
+    u64 oem_platform_rev = 0;
+
+    // get OEM platform revision
+    result = acpi_evaluate_dsm_typed(handle, &MSHW0040_DSM_UUID,
+                     MSHW0040_DSM_REVISION,
+                     MSHW0040_DSM_GET_OMPR,
+                     NULL, ACPI_TYPE_INTEGER);
+

Does it mean, only 5th, 6th and newer platforms have OEM platform revision?
3rd/4th will get NULL result? Or the opposite?

Correct, from my testing (with limited sample size) and AML code: 5th
and 6th generation devices have a non-zero OEM platform revision,
whereas 3rd and 4th gen. devices do not have any (i.e. result will be
NULL).

quoted

quoted

+    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 ? 0 : -ENODEV;

if 3rd/4th do not have this oem rev information while 5th/newer have,
why the latter returns NODEV(it actually has this info)?

Since we always expect a non-zero platform revision (for 5th/6th gen.),
we can initialize it to zero and use that as "unknown"/"not available".
So if it can not be determined, we return NODEV.

Sorry, small mistake here: If it can be determined (i.e. is 5th or 6th
gen.) then we return NODEV. Not the other way around.

How about using a boolean, according to the function name, if a mshw0040 revison
is detected then returns true other wise false. Other than that,
Acked-by: Chen Yu <yu.c.chen@intel.com>

Best,
Chenyu

Also to clarify on your last question:

On 7/2/19 3:14 AM, Yu Chen wrote:

quoted

quoted

  static int surface_button_add(struct acpi_device *device)
  {
  	struct surface_button *button;

@@ -154,6 +188,10 @@ static int surface_button_add(struct acpi_device *device)
  	    strlen(SURFACE_BUTTON_OBJ_NAME)))
  		return -ENODEV;
+	error = surface_button_check_MSHW0040(device);
+	if (error)
+		return error;
+

ditto, 3rd/4th get error=0?

You are correct.

Maximilian