platform/x86: wmi: Prevent incompatible event driver from probing

If a WMI event driver has no_notify_data set, then it indicates
support for WMI events which provide no notify data, otherwise
the notify() callback expects a valid ACPI object as notify data.

However if a WMI event driver which requires notify data is bound
to a WMI event device which cannot retrieve such data due to the
_WED ACPI method being absent, then the driver will be dysfunctional
since all WMI events will be dropped due to the missing notify data.

Fix this by not allowing such WMI event drivers to bind to WMI event
devices which do not support retrieving of notify data. Also reword
the description of no_notify_data a bit.
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20240219115919.16526-2-W_Armin@gmx.deReviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

drivers/platform/x86/wmi.c

@@ -57,6 +57,7 @@ static_assert(__alignof__(struct guid_block) == 1);
 
 enum {	/* wmi_block flags */
 	WMI_READ_TAKES_NO_ARGS,
+	WMI_NO_EVENT_DATA,
 };
 
 struct wmi_block {
@@ -869,6 +870,11 @@ static int wmi_dev_probe(struct device *dev)
 	struct wmi_driver *wdriver = drv_to_wdrv(dev->driver);
 	int ret = 0;
 
+	if (wdriver->notify) {
+		if (test_bit(WMI_NO_EVENT_DATA, &wblock->flags) && !wdriver->no_notify_data)
+			return -ENODEV;
+	}
+
 	if (ACPI_FAILURE(wmi_method_enable(wblock, true)))
 		dev_warn(dev, "failed to enable device -- probing anyway\n");
 
@@ -1094,6 +1100,7 @@ static int parse_wdg(struct device *wmi_bus_dev, struct platform_device *pdev)
 	struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
 	struct acpi_buffer out = {ACPI_ALLOCATE_BUFFER, NULL};
 	const struct guid_block *gblock;
+	bool event_data_available;
 	struct wmi_block *wblock;
 	union acpi_object *obj;
 	acpi_status status;
@@ -1113,6 +1120,7 @@ static int parse_wdg(struct device *wmi_bus_dev, struct platform_device *pdev)
 		return -ENXIO;
 	}
 
+	event_data_available = acpi_has_method(device->handle, "_WED");
 	gblock = (const struct guid_block *)obj->buffer.pointer;
 	total = obj->buffer.length / sizeof(struct guid_block);
 
@@ -1131,6 +1139,8 @@ static int parse_wdg(struct device *wmi_bus_dev, struct platform_device *pdev)
 
 		wblock->acpi_device = device;
 		wblock->gblock = gblock[i];
+		if (gblock[i].flags & ACPI_WMI_EVENT && !event_data_available)
+			set_bit(WMI_NO_EVENT_DATA, &wblock->flags);
 
 		retval = wmi_create_device(wmi_bus_dev, wblock, device);
 		if (retval) {

include/linux/wmi.h

@@ -48,7 +48,7 @@ u8 wmidev_instance_count(struct wmi_device *wdev);
  * struct wmi_driver - WMI driver structure
  * @driver: Driver model structure
  * @id_table: List of WMI GUIDs supported by this driver
- * @no_notify_data: WMI events provide no event data
+ * @no_notify_data: Driver supports WMI events which provide no event data
  * @probe: Callback for device binding
  * @remove: Callback for device unbinding
  * @notify: Callback for receiving WMI events