HID: hidraw: add support uniq ioctl

Add support for reading out the uniq information from the underlying HID
device. This might be the iSerialNumber in case of USB or the BD_ADDR in
case of Bluetooth.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index c3fc0ce..5dfe802 100644
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -450,6 +450,15 @@ static long hidraw_ioctl(struct file *file, unsigned int cmd,
 						-EFAULT : len;
 					break;
 				}
+
+				if (_IOC_NR(cmd) == _IOC_NR(HIDIOCGRAWUNIQ(0))) {
+					int len = strlen(hid->uniq) + 1;
+					if (len > _IOC_SIZE(cmd))
+						len = _IOC_SIZE(cmd);
+					ret = copy_to_user(user_arg, hid->uniq, len) ?
+						-EFAULT : len;
+					break;
+				}
 			}
 
 		ret = -ENOTTY;