I'd need your Xorg.log please and the evtest output from the device.

Created attachment 39180 [details]
Xorg.0.log

Output from evtest:

Input driver version is 1.0.1
Input device ID: bus 0x11 vendor 0x2 product 0x7 version 0x1b1
Input device name: "SynPS/2 Synaptics TouchPad"
Supported events:
  Event type 0 (Sync)
  Event type 1 (Key)
    Event code 272 (LeftBtn)
    Event code 273 (RightBtn)
    Event code 274 (MiddleBtn)
    Event code 277 (ForwardBtn)
    Event code 278 (BackBtn)
    Event code 325 (ToolFinger)
    Event code 330 (Touch)
  Event type 3 (Absolute)
    Event code 0 (X)
      Value      0
      Min     1472
      Max     5888
    Event code 1 (Y)
      Value      0
      Min     1408
      Max     4820
    Event code 24 (Pressure)
      Value      0
      Min        0
      Max      255
    Event code 28 (Tool Width)
      Value      0
      Min        0
      Max        0
Testing ... (interrupt to exit)

Can you look at information in buzilla report #29493?  Especially Comment 6 and 7?

It contains some hints on enabling 2-finger emulation and differences between xf86-input-synaptics-1.2.2 and 1.3.0.

Google shows that your model can use 2-finger emulation.

Thank you for your comments. I looked at it using the xinput tool. In fact, Two-Finger Scrolling was already enabled, but the Two-Finger Pressure was set to a very high value (280). As soon as I lowered it to 10, scrolling with two fingers started working as it should.

So the question is: where does this pressure value come from?

(In reply to comment #4)
> Can you look at information in buzilla report #29493?  Especially Comment 6 and
> 7?
> 
> It contains some hints on enabling 2-finger emulation and differences between
> xf86-input-synaptics-1.2.2 and 1.3.0.
> 
> Google shows that your model can use 2-finger emulation.

(In reply to comment #5)
> Thank you for your comments. I looked at it using the xinput tool. In fact,
> Two-Finger Scrolling was already enabled, but the Two-Finger Pressure was set
> to a very high value (280). As soon as I lowered it to 10, scrolling with two
> fingers started working as it should.

that sounds like a bug. can you try to verify this please and make sure you don't have any configurations hanging around that may modify this? is it always 280?

(In reply to comment #3)
> Supported events:
>   Event type 0 (Sync)
>   Event type 1 (Key)
>     Event code 272 (LeftBtn)
>     Event code 273 (RightBtn)
>     Event code 274 (MiddleBtn)
>     Event code 277 (ForwardBtn)
>     Event code 278 (BackBtn)
>     Event code 325 (ToolFinger)
>     Event code 330 (Touch)

this snippet shows that BTN_TOOL_DOUBLETAP is missing, that's what the driver uses for two-finger capabilities. if the hw supports multifinger natively, the kernel driver needs to support this device. Otherwise, two-finger emulation through width (as Chris said) is the way to go.

I tried with a Fedora 14 daily CD. This has, unlike my Ubuntu Maverick, a sensible default value for the pressure (29). On Ubuntu, this is reproducibly set to 280. Where are those default values set?

On both distributions, the Gnome Touchpad capplet does not offer to enable two-finger scrolling. That may be because the kernel does not support actual two-finger data, which forces the driver to use emulation, which in turn the capplet doesn't support?

So, how can we verify that the issue is really in the kernel, and where do i have to report that?

(In reply to comment #8)
> I tried with a Fedora 14 daily CD. This has, unlike my Ubuntu Maverick, a
> sensible default value for the pressure (29). On Ubuntu, this is reproducibly
> set to 280. Where are those default values set?

default values are calculated in the driver. U has a number of patches against synaptics though, so maybe there's some patch going nuts? don't know. If the stock synaptics driver works fine though, that's a bug you need to file in launchpad.

> On both distributions, the Gnome Touchpad capplet does not offer to enable
> two-finger scrolling. That may be because the kernel does not support actual
> two-finger data, which forces the driver to use emulation, which in turn the
> capplet doesn't support?
> 
> So, how can we verify that the issue is really in the kernel, and where do i
> have to report that?

the evtest output should show BTN_TOOL_DOUBLE ("Tool Double" or so) for two-finger capabilities. if the hardware specs claim multitouch support but the evtest output doesn't show it, then it's a kernel bug and you can report it at http://bugzilla.kernel.org/. Just search for dupes before, I wouldn't surprised if there's already a bug filed for it..


I think this bug is NOTOURBUG though. If I didn't miss anything, we have the Ubuntu bug with the pressure (→ launchpad), the capplet not supporting two-finger emulation (→ bugzilla.gnome.org) and the missing kernel feature (→ bugzilla.kernel.org).

For reference, the issues are tracked in the following bug reports:

Gnome Mouse Capplet: b.g.o #625163

Multitouch support in the kernel: b.k.o #16041

Ubuntu default value issue: LP #648671