HID: core: Add functions for HID drivers to react on first open and last close call

Adds a new function to the hid_driver struct that is called when the
userspace starts using the device, and another one that is called when
userspace stop using the device. With this a hid driver can implement
special suspend handling for devices currently not in use.

Signed-off-by: Werner Sembach <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Benjamin Tissoires <[email protected]>

Author: tuxedo-wse

drivers/hid/hid-core.c

@@ -2396,6 +2396,9 @@ int hid_hw_open(struct hid_device *hdev)
 		ret = hdev->ll_driver->open(hdev);
 		if (ret)
 			hdev->ll_open_count--;
+
+		if (hdev->driver->on_hid_hw_open)
+			hdev->driver->on_hid_hw_open(hdev);
 	}
 
 	mutex_unlock(&hdev->ll_open_lock);
@@ -2415,8 +2418,12 @@ EXPORT_SYMBOL_GPL(hid_hw_open);
 void hid_hw_close(struct hid_device *hdev)
 {
 	mutex_lock(&hdev->ll_open_lock);
-	if (!--hdev->ll_open_count)
+	if (!--hdev->ll_open_count) {
 		hdev->ll_driver->close(hdev);
+
+		if (hdev->driver->on_hid_hw_close)
+			hdev->driver->on_hid_hw_close(hdev);
+	}
 	mutex_unlock(&hdev->ll_open_lock);
 }
 EXPORT_SYMBOL_GPL(hid_hw_close);

include/linux/hid.h

@@ -795,6 +795,8 @@ struct hid_usage_id {
  * @suspend: invoked on suspend (NULL means nop)
  * @resume: invoked on resume if device was not reset (NULL means nop)
  * @reset_resume: invoked on resume if device was reset (NULL means nop)
+ * @on_hid_hw_open: invoked when hid core opens first instance (NULL means nop)
+ * @on_hid_hw_close: invoked when hid core closes last instance (NULL means nop)
  *
  * probe should return -errno on error, or 0 on success. During probe,
  * input will not be passed to raw_event unless hid_device_io_start is
@@ -850,6 +852,8 @@ struct hid_driver {
 	int (*suspend)(struct hid_device *hdev, pm_message_t message);
 	int (*resume)(struct hid_device *hdev);
 	int (*reset_resume)(struct hid_device *hdev);
+	void (*on_hid_hw_open)(struct hid_device *hdev);
+	void (*on_hid_hw_close)(struct hid_device *hdev);
 
 /* private: */
 	struct device_driver driver;