Re: Synaptics Touchpad workaround for strange behavior after Sync loss (With Patch).

[Vojtech Pavlik <vojtech@suse.cz>]

On Sun, Jan 11, 2004 at 01:46:41PM +0100, Peter Berg Larsen wrote:
> 
> On Sun, 11 Jan 2004, Vojtech Pavlik wrote:
> 
> > > 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.
> 
> Are you sure? The i8042_command does spin_lock_irqsave(&i8042_lock,
> flags), i8042_wait_read, i8042_read_data and unlock. It seems a good place
> for me as the 8042s buffer is just flush by the interrupt. Well except for
> the fact it is in the interrupt handler :)

You're right, it's quite safe, but still not very nice, since the lock
fortunately isn't held at the time we would call i8042_command. However,
since i8042_command doesn't disable interrupts globally (only locally),
an interrupt generated by the controller when it acks our command still
can happen on a second CPU. It'll spin on the lock, though.

> I cannot see a simple/fast solution: All data read in the interrupt must
> be processed otherwise kbd data might be lost. I dont want
> I8042_BUFFER_SIZE calls to serio_rescan/reconnect, as serio is not smart
> enought to only do it once.

Check my current version at bk://kernel.bkbits.net/vojtech/input, there
isn't I8042_BUFFER_SIZE cycle in the interrupt routine anymore.

> The mux port number(s) must be remembered if
> serio is called after the loop. I dont like any further calls to
> i8042_flush as it troughs away both kbd and aux data.
> 
> hmm, I actually want the handler to look something like:
> 
>  if (str & I8042_STR_MUXERR)
>           i8042_handle_aux_data
>  else
>           i8042_handle_kbd_data
> 
> That way i8042_flush can call handle_*_data depending on what to flush.

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR