[PATCH 1/2] Add functions for HID drivers to react on first open and last close call

[Werner Sembach <wse@xxxxxxxxxxxxxxxxxxx>]

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 <wse@xxxxxxxxxxxxxxxxxxx>
---
 drivers/hid/hid-core.c | 9 ++++++++-
 include/linux/hid.h    | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 4497b50799dbf..283917a79ac86 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2392,6 +2392,9 @@ 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);
@@ -2411,8 +2414,12 @@ 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);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index cdc0dc13c87fe..3b7db4eb3f2f6 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -790,6 +790,8 @@ 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
@@ -845,6 +847,8 @@ 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;
-- 
2.43.0