HID: logitech-dj: allow devices to request full pairing information

Register 0xB5 should be handled specially no matter what function is
used. This allows to retrieve the serial and the Quad ID from
hid-logitech-hidpp directly.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Tested-by: Bastien Nocera <hadess@hadess.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-logitech-dj.c

@@ -692,8 +692,12 @@ static void logi_dj_ll_close(struct hid_device *hid)
 	dbg_hid("%s:%s\n", __func__, hid->phys);
 }
 
-static u8 unifying_name_query[]  = {0x10, 0xff, 0x83, 0xb5, 0x40, 0x00, 0x00};
-static u8 unifying_name_answer[] = {0x11, 0xff, 0x83, 0xb5};
+/*
+ * Register 0xB5 is "pairing information". It is solely intended for the
+ * receiver, so do not overwrite the device index.
+ */
+static u8 unifying_pairing_query[]  = {0x10, 0xff, 0x83, 0xb5};
+static u8 unifying_pairing_answer[] = {0x11, 0xff, 0x83, 0xb5};
 
 static int logi_dj_ll_raw_request(struct hid_device *hid,
 				  unsigned char reportnum, __u8 *buf,
@@ -712,9 +716,9 @@ static int logi_dj_ll_raw_request(struct hid_device *hid,
 
 		/* special case where we should not overwrite
 		 * the device_index */
-		if (count == 7 && !memcmp(buf, unifying_name_query,
-					  sizeof(unifying_name_query)))
-			buf[4] |= djdev->device_index - 1;
+		if (count == 7 && !memcmp(buf, unifying_pairing_query,
+					  sizeof(unifying_pairing_query)))
+			buf[4] = (buf[4] & 0xf0) | (djdev->device_index - 1);
 		else
 			buf[1] = djdev->device_index;
 		return hid_hw_raw_request(djrcv_dev->hdev, reportnum, buf,
@@ -911,9 +915,8 @@ static int logi_dj_hidpp_event(struct hid_device *hdev,
 		/* special case were the device wants to know its unifying
 		 * name */
 		if (size == HIDPP_REPORT_LONG_LENGTH &&
-		    !memcmp(data, unifying_name_answer,
-			    sizeof(unifying_name_answer)) &&
-		    ((data[4] & 0xF0) == 0x40))
+		    !memcmp(data, unifying_pairing_answer,
+			    sizeof(unifying_pairing_answer)))
 			device_index = (data[4] & 0x0F) + 1;
 		else
 			return false;