platform/x86: wmi: Allow retrieving the number of WMI object instances

Currently, the WMI driver core knows how many instances of a given
WMI object exist, but WMI drivers cannot access this information.
At the same time, some current and upcoming WMI drivers want to
have access to this information. Add wmi_instance_count() and
wmidev_instance_count() to allow WMI drivers to get the number of
WMI object instances.
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20230430203153.5587-2-W_Armin@gmx.deReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/wmi.c

@@ -263,6 +263,47 @@ int set_required_buffer_size(struct wmi_device *wdev, u64 length)
 }
 EXPORT_SYMBOL_GPL(set_required_buffer_size);
 
+/**
+ * wmi_instance_count - Get number of WMI object instances
+ * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
+ *
+ * Get the number of WMI object instances.
+ *
+ * Returns: Number of WMI object instances or negative error code.
+ */
+int wmi_instance_count(const char *guid_string)
+{
+	struct wmi_block *wblock;
+	acpi_status status;
+
+	status = find_guid(guid_string, &wblock);
+	if (ACPI_FAILURE(status)) {
+		if (status == AE_BAD_PARAMETER)
+			return -EINVAL;
+
+		return -ENODEV;
+	}
+
+	return wmidev_instance_count(&wblock->dev);
+}
+EXPORT_SYMBOL_GPL(wmi_instance_count);
+
+/**
+ * wmidev_instance_count - Get number of WMI object instances
+ * @wdev: A wmi bus device from a driver
+ *
+ * Get the number of WMI object instances.
+ *
+ * Returns: Number of WMI object instances.
+ */
+u8 wmidev_instance_count(struct wmi_device *wdev)
+{
+	struct wmi_block *wblock = container_of(wdev, struct wmi_block, dev);
+
+	return wblock->gblock.instance_count;
+}
+EXPORT_SYMBOL_GPL(wmidev_instance_count);
+
 /**
  * wmi_evaluate_method - Evaluate a WMI method (deprecated)
  * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba

include/linux/acpi.h

@@ -414,6 +414,8 @@ extern bool acpi_is_pnp_device(struct acpi_device *);
 
 typedef void (*wmi_notify_handler) (u32 value, void *context);
 
+int wmi_instance_count(const char *guid);
+
 extern acpi_status wmi_evaluate_method(const char *guid, u8 instance,
 					u32 method_id,
 					const struct acpi_buffer *in,

include/linux/wmi.h

@@ -35,6 +35,8 @@ extern acpi_status wmidev_evaluate_method(struct wmi_device *wdev,
 extern union acpi_object *wmidev_block_query(struct wmi_device *wdev,
 					     u8 instance);
 
+u8 wmidev_instance_count(struct wmi_device *wdev);
+
 extern int set_required_buffer_size(struct wmi_device *wdev, u64 length);
 
 /**