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>
---
 drivers/hid/hidraw.c        | 9 +++++++++
 include/uapi/linux/hidraw.h | 1 +
 2 files changed, 10 insertions(+)

diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index bbc6ec1aa5cb..039304069fd0 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;
+				}