Re: [PATCH] Input: serio - clear serio event queue after sysfs driver rebind

[Duncan Laurie <dlaurie@chromium.org>]

On Tue, Feb 1, 2011 at 1:21 AM, Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
> On Tue, Dec 07, 2010 at 09:12:11PM -0800, Dmitry Torokhov wrote:
>> On Mon, Nov 29, 2010 at 01:37:35PM -0800, Duncan Laurie wrote:
>> > On Sat, Nov 27, 2010 at 12:41 AM, Dmitry Torokhov
>> > <dmitry.torokhov@gmail.com> wrote:
>> > > Hi Duncan,
>> > >
>> > > On Mon, Nov 22, 2010 at 03:09:50PM -0800, Duncan Laurie wrote:
>> > >> When rebinding a serio driver via sysfs drvctl interface it is possible for
>> > >> an interrupt to trigger after the disconnect of the existing driver and
>> > >> before the binding of the new driver.  This will cause the serio interrupt
>> > >> handler to queue a rescan event which will disconnect the new driver
>> > >> immediately after it is attached.
>> > >>
>> > >> This change clears the serio event queue after processing the drvctl
>> > >> request but before releasing the serio mutex, which will clear any queued
>> > >> rescans before they can get processed.
>> > >>
>> > >> Reproduction involves issuing a rebind of device port from psmouse driver
>> > >> to serio_raw driver while generating input to trigger interrupts.  Then
>> > >> checking to see if the corresponding i8042/serio4/driver is correctly
>> > >> attached to the serio_raw driver instead of psmouse.
>> > >>
>> > >> Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
>> > >> ---
>> > >>  drivers/input/serio/serio.c |    1 +
>> > >>  1 files changed, 1 insertions(+), 0 deletions(-)
>> > >>
>> > >> diff --git a/drivers/input/serio/serio.c b/drivers/input/serio/serio.c
>> > >> index 405bf21..a66307e 100644
>> > >> --- a/drivers/input/serio/serio.c
>> > >> +++ b/drivers/input/serio/serio.c
>> > >> @@ -454,6 +454,7 @@ static ssize_t serio_rebind_driver(struct device *dev, struct device_attribute *
>> > >>               serio_disconnect_port(serio);
>> > >>               error = serio_bind_driver(serio, to_serio_driver(drv));
>> > >>               put_driver(drv);
>> > >> +             serio_remove_pending_events(serio);
>> > >
>> > > Hmm, makes sense, although should we limit events being removed to
>> > > rescan events only?
>> > >
>> >
>> >
>> > That seems reasonable.  It would mean adding a new function or a
>> > parameter to the existing serio_remove_pending_events function, do you
>> > have a preference?
>> >
>>
>> I wonder if a boolean parameter (rescan_only) would not be the best
>> option.
>>
>
> Hi Duncan,
>
> I eneded up with the following patch, could you please try and see if
> it still works for you?
>


Hi Dmitry,

I tested the patch on a CR-48 device (which is where I was seeing the
problem because we switch to serio_raw at boot for the trackpad) and
it does fix the problem.

Thanks for sending this, it had slipped off my todo list.

-duncan
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