kern/174441: Enable detection of Synaptics touchpad for firmware >= 7.5

[Eygene Ryabinkin]

>Number:         174441
>Category:       kern
>Synopsis:       Enable detection of Synaptics touchpad for firmware >= 7.5
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Dec 14 18:30:00 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Eygene Ryabinkin
>Release:        FreeBSD 10.0-CURRENT amd64
>Organization:
Code Labs
>Environment:

System: FreeBSD 10.0-CURRENT amd64

>Description:

Newer Synaptics touchpads with firmware 7.5 don't put 0x47
to the middle byte for commands 0x01 and 0x02.

>How-To-Repeat:

Get a laptop with new Synaptics (mine was Toshiba Z930) and try to
boot with hw.psm.synaptics_support=1 in loader.conf.  Kernel will
respond with the message "Failed to read extended capability bits"
just before the psm0 device information string.

New manual for Synaptics interface,
  http://www.synaptics.com/sites/default/files/511-000275-01_RevB.pdf
is also helpful to understand what is going on.

>Fix:

I had patched psm.c,
  http://codelabs.ru/fbsd/patches/psm/support-synaptics-firmware-7.5.diff

I had tested it briefly on my laptop and no regressions were found
yet.
>Release-Note:
>Audit-Trail:
>Unformatted: