From a7ef82aee91f26da79b981b9f5bca43b8817d3e4 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Pali=20Roh=C3=A1r?= Date: Sat, 8 Nov 2014 23:36:09 -0800 Subject: [PATCH] Input: alps - ignore bad data on Dell Latitudes E6440 and E7440 MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Sometimes on Dell Latitude laptops psmouse/alps driver receive invalid ALPS protocol V3 packets with bit7 set in last byte. More often it can be reproduced on Dell Latitude E6440 or E7440 with closed lid and pushing cover above touchpad. If bit7 in last packet byte is set then it is not valid ALPS packet. I was told that ALPS devices never send these packets. It is not know yet who send those packets, it could be Dell EC, bug in BIOS and also bug in touchpad firmware... With this patch alps driver does not process those invalid packets, but instead of reporting PSMOUSE_BAD_DATA, getting into out of sync state, getting back in sync with the next byte and spam dmesg we return PSMOUSE_FULL_PACKET. If driver is truly out of sync we'll fail the checks on the next byte and report PSMOUSE_BAD_DATA then. Signed-off-by: Pali Rohár Tested-by: Pali Rohár Cc: stable@vger.kernel.org Signed-off-by: Dmitry Torokhov --- drivers/input/mouse/alps.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c index 433638e..d125a01 100644 --- a/drivers/input/mouse/alps.c +++ b/drivers/input/mouse/alps.c @@ -1186,12 +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; } -- 2.7.4