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-rw-r--r--drivers/input/mouse/alps.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
index 7c5d72a6a26a..071bd835594c 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -873,7 +873,13 @@ 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);