1 files changed, 26 insertions, 2 deletions

diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
index 2b0ae8cc8e51..d125a019383f 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -1156,7 +1156,13 @@ static psmouse_ret_t alps_process_byte(struct psmouse *psmouse)
 {
         struct alps_data *priv = psmouse->private;
 
-        if ((psmouse->packet[0] & 0xc8) == 0x08) { /* PS/2 packet */
+        /*
+         * Check if we are dealing with a bare PS/2 packet, presumably from
+         * a device connected to the external PS/2 port. Because bare PS/2
+         * protocol does not have enough constant bits to self-synchronize
+         * properly we only do this if the device is fully synchronized.
+         */
+        if (!psmouse->out_of_sync_cnt && (psmouse->packet[0] & 0xc8) == 0x08) {
                 if (psmouse->pktcnt == 3) {
                         alps_report_bare_ps2_packet(psmouse, psmouse->packet,
                                                     true);
@@ -1180,12 +1186,27 @@ static psmouse_ret_t alps_process_byte(struct psmouse *psmouse)
         }
 
         /* Bytes 2 - pktsize should have 0 in the highest bit */
-        if ((priv->proto_version < ALPS_PROTO_V5) &&
+        if (priv->proto_version < ALPS_PROTO_V5 &&
             psmouse->pktcnt >= 2 && psmouse->pktcnt <= psmouse->pktsize &&
             (psmouse->packet[psmouse->pktcnt - 1] & 0x80)) {
                 psmouse_dbg(psmouse, "refusing packet[%i] = %x\n",
                             psmouse->pktcnt - 1,
                             psmouse->packet[psmouse->pktcnt - 1]);
+
+                if (priv->proto_version == ALPS_PROTO_V3 &&
+                    psmouse->pktcnt == psmouse->pktsize) {
+                        /*
+                         * Some Dell boxes, such as Latitude E6440 or E7440
+                         * with closed lid, quite often smash last byte of
+                         * otherwise valid packet with 0xff. Given that the
+                         * next packet is very likely to be valid let's
+                         * report PSMOUSE_FULL_PACKET but not process data,
+                         * rather than reporting PSMOUSE_BAD_DATA and
+                         * filling the logs.
+                         */
+                        return PSMOUSE_FULL_PACKET;
+                }
+
                 return PSMOUSE_BAD_DATA;
         }
 
@@ -2389,6 +2410,9 @@ int alps_init(struct psmouse *psmouse)
         /* We are having trouble resyncing ALPS touchpads so disable it for now */
         psmouse->resync_time = 0;
 
+        /* Allow 2 invalid packets without resetting device */
+        psmouse->resetafter = psmouse->pktsize * 2;
+
         return 0;
 
 init_fail: