Patch "Input: psmouse - disable automatic probing of BYD touchpads" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

Input: psmouse - disable automatic probing of BYD touchpads

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
input-psmouse-disable-automatic-probing-of-byd-touchpads.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dmitry Torokhov <[email protected]>
Date: Sat, 12 Nov 2016 10:45:48 -0800
Subject: Input: psmouse - disable automatic probing of BYD touchpads
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From: Dmitry Torokhov <[email protected]>

commit e9fb7cc63801d3dc71b60ca11c4d08f68f879a53 upstream.

BYD automatic protocol detection is extremely unreliable and is often triggers false positives on regular mice, Sentelic touchpads, and other devices. BYD has several documents that have recommended detection sequence, but they conflict with each other and, as far as I can see, still would not produce unique enough output to reliably differentiate BYD from other PS/2 devices.

OEMs sourcing BYD devices also do not do us any favors by not supplying any reasonable DMI data and instead leaving turds like "To Be Filled By O.E.M." in place of vendor data, or "System Serial Number" as serial number.

On top of that BYD is not truly modern multitouch controller, but rather a single-touch transitional device that only reports absolute coordinates at the beginning of finger contact and then reverts to reporting displacements, and thus not very precise; the only benefit from using BYD mode vs the legacy PS/2 mode is possibility of edge scrolling.

Given the above, and the fact that BYD devices are somewhat uncommon, let's disable automatic detection of BYD devices. Users who know they have BYD trackpads or want to experiment can attempt to activate BYD protocol via sysfs:

echo -n "byd" > /sys/bus/serio/devices/serio1/drvctl

---
 drivers/input/mouse/psmouse-base.c |    4 ----
 1 file changed, 4 deletions(-)

@@ -1115,10 +1115,6 @@ static int psmouse_extensions(struct psm
 		if (psmouse_try_protocol(psmouse, PSMOUSE_TOUCHKIT_PS2,
 					 &max_proto, set_properties, true))
 			return PSMOUSE_TOUCHKIT_PS2;
-
-		if (psmouse_try_protocol(psmouse, PSMOUSE_BYD,
-					 &max_proto, set_properties, true))
-			return PSMOUSE_BYD;
 	}
 
 	/*

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/input-change-key_data-from-0x275-to-0x277.patch queue-4.8/input-psmouse-disable-automatic-probing-of-byd-touchpads.patch