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    SubjectRe: Synaptics Touchpad workaround for strange behavior after Sync loss (With Patch).
    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://, 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
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