linux-kernel - Re: Sony Vaio VGN-CS31S touch sensor buttons breaking touchpad

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Date:   Tue, 3 Apr 2018 22:48:16 +0200
From:   Ondrej Zary <linux@...nbow-software.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Sony Vaio VGN-CS31S touch sensor buttons breaking touchpad

On Monday 02 April 2018 22:39:59 Ondrej Zary wrote:
> On Sunday 01 April 2018 23:21:55 Ondrej Zary wrote:
> > Hello,
> > I got a Sony Vaio VGN-CS31S laptop with Synaptics touchpad that exhibits
> > weird behavior. It seems to work until I touch the "Touch Sensor Buttons"
> > bar above the keyboard - then the buttons start to act weirdly: click or
> > remain pressed (sometimes it breaks even without touching the bar).
> >
> > It seems to be a known problem with VGN-CS series:
> > https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-input-synaptics/+b
> >ug /774877
> > https://wiki.freegeekvancouver.org/article/Laptop_Troubleshooting
> > (mentions nasty partial workaround: psmouse.resetafter=1)
> >
> > Many models of the VGN-CS series have the Touch Sensor Buttons:
> > ftp://124.40.41.224/PUB/MANUALS/SWT/Z009/Z009690111.PDF
> >
> > From the hardware side (can be found in MBX-196 Quanta GD2 schematic),
> > the touch bar is a separate PS/2 device connected to third PS/2 port of
> > the EC (Embedded Controller) WPC775L. The touchpad is on the 1st PS/2
> > port, 2nd port is unused. However, the i8042 does not seem to support
> > multiplexing, the firmware probably combines the data internally somehow.
>
> Good news: it supports multiplexing but i8042_nomux is set because of:
>                 /*
>                  * Most (all?) VAIOs do not have external PS/2 ports nor
>                  * they implement active multiplexing properly, and
>                  * MUX discovery usually messes up keyboard/touchpad.
>                  */
>                 .matches = {
>                         DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
>                         DMI_MATCH(DMI_BOARD_NAME, "VAIO"),
>                 },
> in drivers/input/serio/i8042-x86ia64io.h
> (How can this be modified to exclude VGN-CS series?)
>
> Now only to write the touchbar driver... (seems to be detected at serio2 as
> PS/2 Generic Mouse)

The device acts almost as a synaptics touchpad. The 0x47 magic number (used in
detection) is replaced by 0x43.

The absolute packet format is simple:

BYTE  BIT 7 6 5 4 3 2 1 0
  1       1 0 Z Z Z Z Z Z  pressure (left)
  2       0 0 0 0 L L L L  position (left:11-8)
  3       L L L L L L L L  position (left:7-0)
  4       1 1 Z Z Z Z Z Z  pressure (right)
  5       0 0 0 A R R R R  position (right:11-8), A = AV MODE (center "button")
  6       R R R R R R R R  position (right:7-0)

(left = media player part, right = volume part)
maximum observed pressure was 0x38

Now find the command(s) to control the LEDs...

What's the best way to present these controls to user space?
Process the touch/drag actions in kernel. light up corresponding LEDs and
emit key presses?

-- 
Ondrej Zary