$Id: README 720 2012-10-02 00:14:28Z dturvene $
History
-------
0.1: hacked in rudimentary support for the Dell IR15 N5110. Nothing else
should work - probably causing a kernel panic.
0.2: add logic to isolate N5110 changes from previously supported devices
expand diagnostics to capture touchpad protocol
add kernel parameter to enable/disable runtime packet debug
enabled edge scrolling for N5110
add more shell scripts to control/debug device
0.3: clean up a potential null pointer exception
added signature for Dell I17R 7720 based on user confirmaton to V6 protocol
disable multi-touch for V6 protocol
include alps.sh helper scripts
0.4: integrate multi-touch support from florin9doi
default alps_debug=0, can be enabled through sysfs
code cleanup
0.5: elevate persistent syslog to psmouse_info for production/release capture
of alps signature and command response - both of which determine control
protocol
1.2: Try to unify the two V5 init sequences.
How to set up
-------------
cd to the directory where this readme sits.
as root, do:
$ dkms add .
$ modprobe -r psmouse
$ dkms build -m psmouse -v custom-1.2 --all
$ dkms autoinstall --force
$ modprobe psmouse
There is some reporting data in dmesg | grep psmouse
Background
----------
This README documents my work to reverse engineer the Alps touchpad on a
Dell N5110 for Linux. When I first purchased the laptop and installed
Ubuntu 12.04, I noticed that the touchpad behaved erratically. It would
randomly skip and home-to-cursor. A brief search showed that this
behavior has been a long-standing and well publicized issued. To date
several other Alps touchpads have been reverse engineered but no one had
addressed this particular model.
Dell has a driver for the touchpad for Vista and Win7. I repeatedly
contacted Dell support and Alps; the only response I received was "We
don't support Linux"; odd considering Dell ships Ubuntu.
I developed a simple serio_raw program to peek/poke at the touchpad and
found it had characteristics inconsistent with other Alps touchpads. I
used Seth Forshee's procedure to dump the driver interface using qemu and
vista as the guest OS [1]. This require me to patch the qemu
acpi-dsdt.dsl file to recognize the Alps hardware in order to install
the Dell/Alps Vista driver [2]
Based on the qemu log, I started hacking up a psmouse DLKM from the
linux-3.2.0 source tree. First I added in Ben Gamari's ALPS_PROTO_V5
fix for the Alps Touchpad on his Dell E6230 [3] and tried it but the
characteristics were too different. In fact even the enter-command-mode
generic response is different. I then took the vista log and
created an ALPS_PROTO_V6 hw init by pasting the init sequence from the
qemu log into alps_hw_init_v6. That got me part of the way, the device
was no longer being handled as a stock ps/2 mouse but now as an ALPS
DualPoint Touchpad. However, the 6-byte message format was undocumented
[4]. As far as I can tell, it is:
byte 0: 1 1 0 0 1 0 0 0
byte 1: 0 x6 x5 x4 x3 x2 x1 x0
byte 2: 0 y6 y5 y4 y3 y2 y1 y0
byte 3: 0 ? ? ? 1 m r l
byte 4: y10 y9 y8 y7 x10 x9 x8 x7
byte 5: 0 z6 z5 z4 z3 z2 z1 z0
So I created alps_process_touchpad_packet_v6 to parse the touchpad
packets.
The ALPS touchpad is working on my N5110. I can control the touchpad
somewhat via xinput and the System Settings->Touchpad widget. I think
it can still be tightened up but, at least, it's usable now.
Dave Turvene
[1] http://swapspace.forshee.me/2011/11/touchpad-protocol-reverse-engineering.html
[2] http://www.spinics.net/lists/linux-input/msg21948.html
[3] http://www.spinics.net/lists/linux-input/msg21993.html
[4] file:///usr/src/linux-source-3.2.0/linux-3.2.0/Documentation/input/alps.txt
bash shell scripts
------------------
See alps.sh for support scripts.