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>

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;

include/uapi/linux/hidraw.h

@@ -39,6 +39,7 @@ struct hidraw_devinfo {
 /* The first byte of SFEATURE and GFEATURE is the report number */
 #define HIDIOCSFEATURE(len)    _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x06, len)
 #define HIDIOCGFEATURE(len)    _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x07, len)
+#define HIDIOCGRAWUNIQ(len)     _IOC(_IOC_READ, 'H', 0x08, len)
 
 #define HIDRAW_FIRST_MINOR 0
 #define HIDRAW_MAX_DEVICES 64