[3.13.y-ckt stable] Patch "Input: alps - ignore bad data on Dell Latitudes E6440 and E7440" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    Input: alps - ignore bad data on Dell Latitudes E6440 and E7440

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From ee191b365a6f459cae24bdccbcf25131c0b1d02c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pali=20Roh=C3=A1r?= <pali.rohar at gmail.com>
Date: Sat, 8 Nov 2014 23:36:09 -0800
Subject: Input: alps - ignore bad data on Dell Latitudes E6440 and E7440
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit a7ef82aee91f26da79b981b9f5bca43b8817d3e4 upstream.

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 <pali.rohar at gmail.com>
Tested-by: Pali Rohár <pali.rohar at gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov at gmail.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 00544a6..b1385f0 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -993,12 +993,27 @@ 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;
 	}

--
1.9.1