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SubjectRe: Synaptics Touchpad workaround for strange behavior after Sync loss (With Patch).
On Sat, Jan 10, 2004 at 11:50:02PM +0100, Peter Berg Larsen wrote:

> On Fri, 9 Jan 2004, Vojtech Pavlik wrote:
> > The sync problems have so far been found to be caused by two possible
> > causes:
> >
> > 1) Too long disabled interrupts. This is usually caused by ACPI
> > BIOS, when some application is polling for battery status
> > too often.
> >
> > 2) Incorrectly working timer (jiffies). This maybe caused by
> > using the ACPI timer instead of the regular PIT one. Check
> > the config.
> >
> > Both these causes break the lost bytes detection mechanism in the ps/2
> > code. It then thinks that a byte was lost (and thus the sync, too), but
> > in reality everything is OK. This in turn causes two consecutive
> > incorrectly parsed packets.
> I also believe some of the troubles comes from that we never check all
> error codes from the mux: If mux is disabled for some reason all bytes are
> stamped as timed out. The only way to recover is to reboot. And (I am
> speculating here) if for some reason the mux believe the touchpad is
> removed and connected the touchpad sends 2 bytes ack.
> I dont have a machine with active multiplexing so the the patch is
> untested. It warns when the mouse is removed, and tries to recover
> if multiplexing is disabled.

It's nice, but er definitely shouldn't call i8042_enable_mux() from the
interrupt handler, because i8042_command() waits for characters arriving
in the interrupt handler, so we could get into rather nasty recursions.

Vojtech Pavlik
SuSE Labs, SuSE CR
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