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I'm on a MacBook2,1, running a fully updated Ubuntu 12.04. When using
the internal Touchpad (appletouch driver), the cursor only moves
horizontally or vertically. When dragging a diagonal line, the cursor
will move in steps, basically rendering the builtin touchpad unusable.
This issue is also described in a forum thread:
http://ubuntuforums.org/showthread.php?t=813884&page=6

WORKAROUND: In precise, in the second post on page 6 describes a solution. In the linux kernel, in appletouch.c, change the following two defines and recompile:
Original:
#define ATP_FUZZ 16
#define ATP_THRESHOLD 5

New:
#define ATP_FUZZ 0
#define ATP_THRESHOLD 3

I tried this and can confirm that the touchpad is now fully usable.
However, recompiling the kernel takes several hours and *all* of the
disk space on my laptop. Doing this on every kernel update is just not
practical. I would therefore like to ask that this be applied as a patch
to the default ubuntu kernel. At the very least, please make an optional
package containing the patched appletouch driver that can be selectively
installed by people having this issue.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-generic 3.2.0.27.29
ProcVersionSignature: Ubuntu 3.2.0-27.43-generic 3.2.21
Uname: Linux 3.2.0-27-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu12
Architecture: amd64
AudioDevicesInUse:
 USER        PID ACCESS COMMAND
 /dev/snd/controlC0:  damian     1778 F.... pulseaudio
CRDA:
 country AW:
  (2402 - 2482 @ 40), (N/A, 20)
  (5170 - 5250 @ 40), (N/A, 20)
  (5250 - 5330 @ 40), (N/A, 20), DFS
  (5490 - 5710 @ 40), (N/A, 27), DFS
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0x90440000 irq 43'
   Mixer name	: 'SigmaTel STAC9221 A1'
   Components	: 'HDA:83847680,106b2200,00103401'
   Controls      : 25
   Simple ctrls  : 13
Date: Tue Aug  7 21:35:12 2012
HibernationDevice: RESUME=UUID=a7716e7d-8718-4fe9-988f-958519d6a2c2
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64+mac (20120425.1)
MachineType: Apple Inc. MacBook2,1
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-27-generic root=UUID=c63dd388-29f9-43dc-a835-0b471ccb2f85 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.2.0-27-generic N/A
 linux-backports-modules-3.2.0-27-generic  N/A
 linux-firmware                            1.79
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 06/27/07
dmi.bios.vendor: Apple Inc.
dmi.bios.version: MB21.88Z.00A5.B07.0706270922
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: Mac-F4208CA9
dmi.board.vendor: Apple Inc.
dmi.board.version: PVT
dmi.chassis.asset.tag: Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: Apple Inc.
dmi.chassis.version: Mac-F4208CA9
dmi.modalias: dmi:bvnAppleInc.:bvrMB21.88Z.00A5.B07.0706270922:bd06/27/07:svnAppleInc.:pnMacBook2,1:pvr1.0:rvnAppleInc.:rnMac-F4208CA9:rvrPVT:cvnAppleInc.:ct10:cvrMac-F4208CA9:
dmi.product.name: MacBook2,1
dmi.product.version: 1.0
dmi.sys.vendor: Apple Inc.

** Affects: linux
     Importance: Undecided
         Status: New

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug kernel-bug-exists-upstream needs-upstream-testing precise quantal raring running-unity
-- 
[MacBook2,1] Touchpad cursor moving in steps
https://bugs.launchpad.net/bugs/1034132
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