On 7/2/19 3:14 AM, Yu Chen wrote:
On Tue, Jul 02, 2019 at 02:37:39AM +0200, Maximilian Luz wrote:+/* + * 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).
+ 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.
+}
Cheers, Maximilian
