Input: uinput - add UI_GET_VERSION ioctl

This ioctl is the counterpart to EVIOCGVERSION and returns the
uinput-version the kernel was compiled with.

Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/uinput.c

@@ -723,6 +723,12 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
 	}
 
 	switch (cmd) {
+		case UI_GET_VERSION:
+			if (put_user(UINPUT_VERSION,
+				     (unsigned int __user *)p))
+				retval = -EFAULT;
+			goto out;
+
 		case UI_DEV_CREATE:
 			retval = uinput_create_device(udev);
 			goto out;

include/uapi/linux/uinput.h

@@ -84,6 +84,15 @@ struct uinput_ff_erase {
  */
 #define UI_GET_SYSNAME(len)	_IOC(_IOC_READ, UINPUT_IOCTL_BASE, 300, len)
 
+/**
+ * UI_GET_VERSION - Return version of uinput protocol
+ *
+ * This writes uinput protocol version implemented by the kernel into
+ * the integer pointed to by the ioctl argument. The protocol version
+ * is hard-coded in the kernel and is independent of the uinput device.
+ */
+#define UI_GET_VERSION		_IOR(UINPUT_IOCTL_BASE, 301, unsigned int)
+
 /*
  * To write a force-feedback-capable driver, the upload_effect
  * and erase_effect callbacks in input_dev must be implemented.