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    SubjectRe: Multitouch regression in 3.3 on thinkpad X220 clickpad
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    On Fri, Apr 20, 2012 at 1:21 AM, Benjamin Herrenschmidt
    <benh@kernel.crashing.org> wrote:
    > So Peter and I have been discussing a problem I observed on my brand new
    > ThinkPad X220 and it's multitouch "clickpad". I've been digging a bit
    > more today and bisected the regression to:
    >
    > commit 7968a5dd492ccc38345013e534ad4c8d6eb60ed1
    > Input: synaptics - add support for Relative mode
    >
    > Without that commit, I can draw two "traces" when using two fingers in
    > mtview (after removing the device from X), each follow one finger.
    >
    > With that commit applied, this doesn't work anymore: it appears to be
    > unable to track more than one finger. IE. If i put a finger on the
    > touchpad, I can draw, but a second finger is then ignored (or causes one
    > or two spots in a random place to appear but that's about it).
    >
    > Now other multitouch operations such as two finger scrolling seem to
    > work in X. I'm not familiar with the inner workings of the input layer
    > or the synaptic touchpads. I'll dig a bit more this week-end if I have
    > time, but it would save me plenty of that precious time if you guys
    > could hint me at things to look at :-)

    Sorry to cause you this trouble.
    It's the first I've heard of issues with this patch, and unfortunately
    I don't have any immediate diagnosis for you.
    The patch isn't supposed to change behaviour of the existing default
    mode which is called "absolute mode".

    What I would suggest looking at is
    synaptics_set_advanced_gesture_mode(). Is this being called, does it
    run to completion?
    You could also look at the the values passed to synaptics_mode_cmd() -
    how do they compare from good and bad drivers?

    Does this line change over good/bad drivers?
    psmouse serio1: synaptics: Touchpad model: 1, fw: 8.0, id: 0x1e2b1,
    caps: 0xd001a3/0x940300/0x120c00

    Another approach may be to compare the communication with the device
    between good and bad drivers. This can be done with
    echo 1 > /sys/module/i8042/parameters/debug

    The device specs are public and remarkably good:
    http://www.synaptics.com/sites/default/files/511-000275-01_RevB.pdf

    Daniel


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