[PATCH v3 1/6] platform/x86: lenovo-wmi-helpers: Convert returned 4B buffer into u32

[Rong Zhang]

The Windows WMI-ACPI driver converts all ACPI objects into a common
buffer format, so returning a buffer with four bytes will look like an
integer for WMI consumers under Windows.

Therefore, some devices may simply implement the corresponding ACPI
methods to always return a buffer. While lwmi_dev_evaluate_int() expects
an integer (u32), convert returned 4-byte buffer into u32 to support
these devices.

Suggested-by: Armin Wolf <W_Armin@xxxxxx>
Link: https://lore.kernel.org/r/f1787927-b655-4321-b9d9-bc12353c72db@xxxxxx/
Signed-off-by: Rong Zhang <i@xxxxxxxx>
Reviewed-by: Derek J. Clark <derekjohn.clark@xxxxxxxxx>
Tested-by: Derek J. Clark <derekjohn.clark@xxxxxxxxx>
---
Changes in v2:
- New patch (thanks Armin Wolf)
---
 drivers/platform/x86/lenovo/wmi-helpers.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/lenovo/wmi-helpers.c b/drivers/platform/x86/lenovo/wmi-helpers.c
index f6fef6296251..f3bc92ac505a 100644
--- a/drivers/platform/x86/lenovo/wmi-helpers.c
+++ b/drivers/platform/x86/lenovo/wmi-helpers.c
@@ -59,10 +59,25 @@ int lwmi_dev_evaluate_int(struct wmi_device *wdev, u8 instance, u32 method_id,
 		if (!ret_obj)
 			return -ENODATA;
 
-		if (ret_obj->type != ACPI_TYPE_INTEGER)
-			return -ENXIO;
+		switch (ret_obj->type) {
+		/*
+		 * The ACPI method may simply return a 4-byte buffer when a u32
+		 * integer is expected. This is valid on Windows as its WMI-ACPI
+		 * driver converts everything to a common buffer.
+		 */
+		case ACPI_TYPE_BUFFER: {
+			if (ret_obj->buffer.length != 4)
+				return -ENXIO;
 
-		*retval = (u32)ret_obj->integer.value;
+			*retval = *((u32 *)ret_obj->buffer.pointer);
+			return 0;
+		}
+		case ACPI_TYPE_INTEGER:
+			*retval = (u32)ret_obj->integer.value;
+			return 0;
+		default:
+			return -ENXIO;
+		}
 	}
 
 	return 0;
-- 
2.51.0