[PATCH 3.16 026/217] HID: fix hid_ignore_special_drivers module parameter

[Ben Hutchings]

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>

commit 4392bf333388cabdad5afe5b1500002d7b9c318e upstream.

hid_ignore_special_drivers works fine until hid_scan_report autodetects and
reassign devices (for hid-multitouch, hid-microsoft and hid-rmi).

Simplify the handling of the parameter: if it is there, use hid-generic, no
matter what, and if not, scan the device or rely on the hid_have_special_driver
table.

This was detected while trying to disable hid-multitouch on a Surface Pro cover
which prevented to use the keyboard.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/hid/hid-core.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2531,9 +2531,10 @@ int hid_add_device(struct hid_device *hd
 	/*
 	 * Scan generic devices for group information
 	 */
-	if (hid_ignore_special_drivers ||
-	    (!hdev->group &&
-	     !hid_match_id(hdev, hid_have_special_driver))) {
+	if (hid_ignore_special_drivers) {
+		hdev->group = HID_GROUP_GENERIC;
+	} else if (!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);