On Mon, Feb 24, 2014 at 10:03:59PM +0100, Jonas Ådahl wrote:
> On Mon, Feb 24, 2014 at 09:44:34AM +1000, Peter Hutterer wrote:
> > On Sat, Feb 22, 2014 at 04:44:06PM +0100, Jonas Ådahl wrote:
> > > On Tue, Feb 18, 2014 at 04:09:10PM +1000, Peter Hutterer wrote:
> > > > This gives us the ability to handle SYN_DROPPED transparently to the
> > > > caller.
> > > >
> > > > Signed-off-by: Peter Hutterer <peter.hutte...@who-t.net>
> > > > ---
> > > > src/evdev.c | 90
> > > > +++++++++++++++++++++++++++++++++++++++----------------------
> > > > 1 file changed, 58 insertions(+), 32 deletions(-)
> > > >
> > > > diff --git a/src/evdev.c b/src/evdev.c
> > > > index ba28fc6..836d0af 100644
> > > > --- a/src/evdev.c
> > > > +++ b/src/evdev.c
> > > > @@ -29,7 +29,7 @@
> > > > #include <linux/input.h>
> > > > #include <unistd.h>
> > > > #include <fcntl.h>
> > > > -#include <mtdev.h>
> > > > +#include <mtdev-plumbing.h>
> > > > #include <assert.h>
> > > >
> > > > #include "libinput.h"
> > > > @@ -436,56 +436,82 @@ fallback_dispatch_create(void)
> > > > return dispatch;
> > > > }
> > > >
> > > > -static void
> > > > -evdev_process_events(struct evdev_device *device,
> > > > - struct input_event *ev, int count)
> > > > +static inline void
> > > > +evdev_process_event(struct evdev_device *device, struct input_event *e)
> > > > {
> > > > struct evdev_dispatch *dispatch = device->dispatch;
> > > > - struct input_event *e, *end;
> > > > - uint32_t time = 0;
> > > > + uint32_t time = e->time.tv_sec * 1000 + e->time.tv_usec / 1000;
> > > >
> > > > - e = ev;
> > > > - end = e + count;
> > > > - for (e = ev; e < end; e++) {
> > > > - time = e->time.tv_sec * 1000 + e->time.tv_usec / 1000;
> > > > + dispatch->interface->process(dispatch, device, e, time);
> > > > +}
> > > >
> > > > - dispatch->interface->process(dispatch, device, e, time);
> > > > +static inline void
> > > > +evdev_device_dispatch_one(struct evdev_device *device,
> > > > + struct input_event *ev)
> > > > +{
> > > > + if (!device->mtdev) {
> > > > + evdev_process_event(device, ev);
> > > > + } else {
> > > > + mtdev_put_event(device->mtdev, ev);
> > > > + if (libevdev_event_is_code(ev, EV_SYN, SYN_REPORT)) {
> > > > + while(!mtdev_empty(device->mtdev)) {
>
> Nit (coding style): space between while and (
amended, thanks.
..
> > > > static void
> > > > evdev_device_dispatch(void *data)
> > > > {
> > > > struct evdev_device *device = data;
> > > > struct libinput *libinput = device->base.seat->libinput;
> > > > - int fd = device->fd;
> > > > - struct input_event ev[32];
> > > > - int len;
> > > > + struct input_event ev;
> > > > + int rc;
> > > >
> > > > /* If the compositor is repainting, this function is called
> > > > only once
> > > > * per frame and we have to process all the events available on
> > > > the
> > > > * fd, otherwise there will be input lag. */
> > > > do {
> > > > - if (device->mtdev)
> > > > - len = mtdev_get(device->mtdev, fd, ev,
> > > > - ARRAY_LENGTH(ev)) *
> > > > - sizeof (struct input_event);
> > > > - else
> > > > - len = read(fd, &ev, sizeof ev);
> > > > + rc = libevdev_next_event(device->evdev,
> > > > + LIBEVDEV_READ_FLAG_NORMAL,
> > > > &ev);
> > > > + if (rc == LIBEVDEV_READ_STATUS_SYNC) {
> > > > + /* send one more sync event so we handle all
> > > > + currently pending events before we sync up
> > > > + to the current state */
> > > > + ev.code = SYN_REPORT;
> > > > + evdev_device_dispatch_one(device, &ev);
> > >
> > > Is this really correct? Shouldn't calling libevdev_next_event() in SYNC
> > > mode return a SYN_REPORT event as part of the synchronization? If we do
> > > like this it looks like we might "cut" one series of events that would
> > > otherwise be grouped using SYN_REPORT in half.
> >
> > I think you may have misread the diff, this code is only ever called once,
> > on the SYN_DROPPED, all the other events are handled in evdev_sync_device().
> >
> > libevdev guarantees that the event you pass in when you get
> > LIBEVDEV_READ_STATUS_SYNC is the SYN_DROPPED event that triggered the sync.
> > All we do here is change from EV_SYN/SYN_DROPPED to EV_SYN/SYN_REPORT and
> > process that normally. That finishes the current event sequence.
> >
> > We then call evdev_sync_device() which empties and processes the sync queue
> > until -EAGAIN. That queue is also guaranteed to end with a
> > EV_SYN/SYN_REPORT. Once that is done, we jump back here and continue with
> > the loop, which now hopefully has SUCCESS on the next read.
>
> My concern is not that we would add several extra SYN_REPORT splitting
> event series when synchronizing, but that when we have reached the state
> where libevdev_next_event() returns LIBEVDEV_READ_STATUS_SYNC, we might
> be in progress of queuing up a series of events waiting for the next
> SYN_REPORT. What the documentation[0] states regarding this is that all
> events up and including the next SYN_REPORT should be ignored and the
> device should be synchronized. The way I'm reading that is when we reach
> SYN_DROPPED, we should wait with flushing the queue until we can
> synchronize and can provide a more complete state. However, we could as
> well in this case end up with multiple events with the same time in the
> same series (for example if we already queued ABS_X but x has since then
> changed, which would mean we'd have two ABS_X in the same series) so I
> guess its not really better to not flush there.
I think the documentation is a bit off here. As of 3.7
(4369c64c79a22b98d3b7eff9d089196cd878a10a) events are now
atomic, the kernel doesn't write until the SYN_REPORT is ready so there
aren't any events left that we haven't read yet. the documentation predates
that commit (2.6.39).
The only exception is SYN_REPORT with value 1 which I've been told doesn't
really happen anymore and in any way should be handled within libevdev, so
we don't need to cater for it here.
> So, in other words, Reviewed-by: Jonas Ådahl <jad...@gmail.com>
thanks, much appreciated.
Cheers,
Peter
>
> [0] https://www.kernel.org/doc/Documentation/input/event-codes.txt
>
> >
> > > >
> > > > - if (len < 0 || len % sizeof ev[0] != 0) {
> > > > - if (len < 0 && errno != EAGAIN && errno !=
> > > > EINTR) {
> > > > - libinput_remove_source(libinput,
> > > > - device->source);
> > > > - device->source = NULL;
> > > > - }
> > > > + rc = evdev_sync_device(device);
> >
> > ^^^ this is where the actual sync happens
> >
> > > > + if (rc == 0)
> > > > + rc = LIBEVDEV_READ_STATUS_SUCCESS;
> >
> >
> > > > + } else if (rc == LIBEVDEV_READ_STATUS_SUCCESS)
> > > > + evdev_device_dispatch_one(device, &ev);
> > >
> > > nit: if any branch of an if have braces, all should.
> >
> > amended, thanks.
> >
> > Cheers,
> > Peter
> >
> > > > + } while (rc == LIBEVDEV_READ_STATUS_SUCCESS);
> > > >
> > > > - return;
> > > > - }
> > > > -
> > > > - evdev_process_events(device, ev, len / sizeof ev[0]);
> > > > -
> > > > - } while (len > 0);
> > > > + if (rc != -EAGAIN && rc != -EINTR) {
> > > > + libinput_remove_source(libinput, device->source);
> > > > + device->source = NULL;
> > > > + }
> > > > }
> > > >
> > > > static int
> > > > --
> > > > 1.8.4.2
> > >
> > >
> > > Jonas
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