Re: ALPS v7 trackpad passthrough to Thinkpad trackpoint

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Thu, Aug 13, 2015 at 01:03:17PM +0200, Pali Rohár wrote:
> On Friday 07 August 2015 12:35:33 Ari Entlich wrote:
> > On Fri, Aug 7, 2015 at 10:12 AM, Pali Rohár <pali.rohar@gmail.com> wrote:
> > > For some old ALPS devices which use V1 and V2 protocols (with flag
> > > ALPS_PASS) there is something like that. On that devices touchpad is
> > > behind trackpoint HW. But you cannot wait for data or poll for both
> > > devices at same time -- you need to choose if tou want to talk directly
> > > to touchpad (via passthrough mode) or just to trackpoint. I think
> > > because of this limitation ALPS driver implement all logic in one
> > > driver...
> > >
> > > Above was for old ALPS devices. New ALPS devices with V3 or V5 protocols
> > > have trackpoint behind touchpad, so normally OS communicate with
> > > touchpad (and not with trackstick like before). But here touchpad sends
> > > data for both touchpad and trackstick events and so OS does not have
> > > normal access to "hidden" trackstick.
> > >
> > > There is a way "jump" into passthrough mode and talk directly to
> > > trackpoint. But it is used only for configuring trackstick and currently
> > > it is used to configure trackstick so it send data (via touchpad) in
> > > format which is supported by our ALPS driver.
> > >
> > > On the other hand, synaptics driver and devices support full
> > > "encapsulation" or how can I call it of serio PS/2 device and in this
> > > case you can use full set of PS/2 commands directly with trackstick
> > > (behind synaptics touchpad). ALPS devices do not support something like
> > > that.
> > 
> > It looks to me like the Synaptics passthrough is implemented primarily
> > via the ability to write directly to the trackpoint. Events coming
> > from the trackpoint are implemented similarly to the ALPS driver - by
> > redirecting trackpoint events to the second device which the driver
> > creates for the trackpoint.
> > 
> 
> No, passthrough for ALPS and Synaptics differ. Synaptics driver exports
> full serio PS/2 bus on which can be attached psmouse.ko driver with full
> mouse detection (or any other serio driver) and so there can be full
> TPPS/2 trackpoint.c protocol driver.
> 
> ALPS allows us for *some* protocol version passthrough data directly to
> touchpad (or trackpoint) device. There is no support to exporting full
> serio bus with PS/2 access to it (like for Synaptics hardware).

At least we do not know how to detect and activate it even if it exists.

Let's add some ALPS people to the thread: maybe they could share some
details on accessing trackpoints behind the touchpads with us.

Thanks.

-- 
Dmitry
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