HID: Extend the interface with wait io request

Some drivers need to wait for an io from the underlying device, creating
an unwanted dependency on the underlying transport layer. This patch adds
wait() to the interface, thereby removing usbhid from the lion share of
the drivers.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/usbhid/hid-core.c

@@ -1264,6 +1264,7 @@ static struct hid_ll_driver usb_hid_driver = {
 	.power = usbhid_power,
 	.hidinput_input_event = usb_hidinput_input_event,
 	.request = usbhid_request,
+	.wait = usbhid_wait_io,
 };
 
 static int usbhid_probe(struct usb_interface *intf, const struct usb_device_id *id)

include/linux/hid.h

@@ -663,6 +663,7 @@ struct hid_driver {
  * @parse: this method is called only once to parse the device data,
  *	   shouldn't allocate anything to not leak memory
  * @request: send report request to device (e.g. feature report)
+ * @wait: wait for buffered io to complete (send/recv reports)
  */
 struct hid_ll_driver {
 	int (*start)(struct hid_device *hdev);
@@ -681,6 +682,8 @@ struct hid_ll_driver {
 	void (*request)(struct hid_device *hdev,
 			struct hid_report *report, int reqtype);
 
+	int (*wait)(struct hid_device *hdev);
+
 };
 
 #define	PM_HINT_FULLON	1<<5
@@ -903,6 +906,17 @@ static inline void hid_hw_request(struct hid_device *hdev,
 		hdev->ll_driver->request(hdev, report, reqtype);
 }
 
+/**
+ * hid_hw_wait - wait for buffered io to complete
+ *
+ * @hdev: hid device
+ */
+static inline void hid_hw_wait(struct hid_device *hdev)
+{
+	if (hdev->ll_driver->wait)
+		hdev->ll_driver->wait(hdev);
+}
+
 int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, int size,
 		int interrupt);