[3.16.y-ckt stable] Patch "Input: alps - allow up to 2 invalid packets without resetting device" has been added to staging queue

[Luis Henriques]

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

    Input: alps - allow up to 2 invalid packets without resetting device

to the linux-3.16.y-queue branch of the 3.16.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-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt2.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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>From 50ffa6dac518547bf291a7630321f9f7ed1399fa 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 12:58:57 -0800
Subject: Input: alps - allow up to 2 invalid packets without resetting device
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit 9d720b34c0a432639252f63012e18b0507f5b432 upstream.

On some Dell Latitude laptops ALPS device or Dell EC send one invalid byte
in 6 bytes ALPS packet. In this case psmouse driver enter out of sync
state. It looks like that all other bytes in packets are valid and also
device working properly. So there is no need to do full device reset, just
need to wait for byte which match condition for first byte (start of
packet). Because ALPS packets are bigger (6 or 8 bytes) default limit is
small.

This patch increase number of invalid bytes to size of 2 ALPS packets which
psmouse driver can drop before do full reset.

Resetting ALPS devices take some time and when doing reset on some Dell
laptops touchpad, trackstick and also keyboard do not respond. So it is
better to do it only if really necessary.

Signed-off-by: Pali Rohár <pali.rohar at gmail.com>
Tested-by: Pali Rohár <pali.rohar at gmail.com>
Reviewed-by: Hans de Goede <hdegoede at redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov at gmail.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/input/mouse/alps.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
index 873c0e024889..fdffac9f741d 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -2154,6 +2154,9 @@ 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:
--
2.1.0