HID: core: do not scan reports if the group is already set

commit 9578f41a upstream.

This allows the transport layer (I have in mind hid-logitech-dj and uhid)
to set the group before it is added to the hid bus. This way, it can
bypass the hid_scan_report() call, and choose in advance which driver
will handle the newly created hid device.
Signed-off-by: Benjamin Tisssoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/hid/hid-core.c

@@ -2532,7 +2532,8 @@ int hid_add_device(struct hid_device *hdev)
 	 * Scan generic devices for group information
 	 */
 	if (hid_ignore_special_drivers ||
-	    !hid_match_id(hdev, hid_have_special_driver)) {
+	    (!hdev->group &&
+	     !hid_match_id(hdev, hid_have_special_driver))) {
 		ret = hid_scan_report(hdev);
 		if (ret)
 			hid_warn(hdev, "bad device descriptor (%d)\n", ret);