HID: wiimote: lock DRM mode during debugfs overwrite

If we write a DRM mode via debugfs, we shouldn't allow normal operations
to overwrite this DRM mode. This is important if we want to debug
3rd-party devices and we want to see what data is sent on each mode.

If we write NULL/0 as DRM, the lock is removed again so the best matching
DRM is chosen by wiimote core.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-wiimote-core.c b/drivers/hid/hid-wiimote-core.c
index f6c4773..13963b4 100644
--- a/drivers/hid/hid-wiimote-core.c
+++ b/drivers/hid/hid-wiimote-core.c
@@ -242,7 +242,9 @@
 {
 	__u8 cmd[3];
 
-	if (drm == WIIPROTO_REQ_NULL)
+	if (wdata->state.flags & WIIPROTO_FLAG_DRM_LOCKED)
+		drm = wdata->state.drm;
+	else if (drm == WIIPROTO_REQ_NULL)
 		drm = select_drm(wdata);
 
 	cmd[0] = WIIPROTO_REQ_DRM;