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Switch to a state machine to handle incomplete syncs

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A caller may start syncing but switch back to normal half-way through the
sync. In that case, we need to drop all sync events and continue with
regular events only.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
This commit is contained in:
Peter Hutterer 2013-07-02 10:50:37 +10:00
parent f3a6b0c685
commit c661e80ba0
2 changed files with 39 additions and 11 deletions
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19
libevdev/libevdev-int.h
View file

@ -51,6 +51,23 @@
_a > _b ? _a : _b; \
})
/**
* Sync state machine:
* default state: SYNC_NONE
*
* SYNC_NONE → SYN_DROPPED or forced sync → SYNC_NEEDED
* SYNC_NEEDED → libevdev_next_event(LIBEVDEV_READ_SYNC) → SYNC_IN_PROGRESS
* SYNC_NEEDED → libevdev_next_event(LIBEVDEV_READ_SYNC_NONE) → SYNC_NONE
* SYNC_IN_PROGRESS → libevdev_next_event(LIBEVDEV_READ_SYNC_NONE) → SYNC_NONE
* SYNC_IN_PROGRESS → no sync events left → SYNC_NONE
*
*/
enum SyncState {
SYNC_NONE,
SYNC_NEEDED,
SYNC_IN_PROGRESS,
};
struct libevdev {
int fd;
libevdev_log_func_t log;
@ -78,7 +95,7 @@ struct libevdev {
int current_slot;
int rep_values[2];
int need_sync;
enum SyncState sync_state;
int grabbed;
struct input_event *queue;

31
libevdev/libevdev.c
View file

@ -74,6 +74,7 @@ libevdev_new(void)
dev->current_slot = -1;
dev->log = libevdev_noop_log_func;
dev->grabbed = LIBEVDEV_UNGRAB;
dev->sync_state = SYNC_NONE;
return dev;
}
@ -401,7 +402,7 @@ sync_state(struct libevdev *dev)
/* FIXME: if we have events in the queue after the SYN_DROPPED (which was
queue[0]) we need to shift this backwards. Except that chances are that the
queue may be either full or too full to prepend all the events needed for
syncing.
SYNC_IN_PROGRESS.
so we search for the last sync event in the queue and drop everything before
including that event and rely on the kernel to tell us the right value for that
@ -429,7 +430,6 @@ sync_state(struct libevdev *dev)
init_event(dev, ev, EV_SYN, SYN_REPORT, 0);
dev->queue_nsync = queue_num_elements(dev);
dev->need_sync = 0;
return rc;
}
@ -540,23 +540,32 @@ int libevdev_next_event(struct libevdev *dev, unsigned int flags, struct input_e
return -EINVAL;
if (flags & LIBEVDEV_READ_SYNC) {
if (!dev->need_sync && dev->queue_nsync == 0)
return -EAGAIN;
else if (dev->need_sync) {
if (dev->sync_state == SYNC_NEEDED) {
rc = sync_state(dev);
if (rc != 0)
return rc;
dev->sync_state = SYNC_IN_PROGRESS;
}
} else if (dev->need_sync) {
if (dev->queue_nsync == 0) {
dev->sync_state = SYNC_NONE;
return -EAGAIN;
}
} else if (dev->sync_state != SYNC_NONE) {
struct input_event e;
/* call update_state for all events here, otherwise the library has the wrong view
of the device too */
while (queue_shift(dev, &e) == 0)
while (queue_shift(dev, &e) == 0) {
dev->queue_nsync--;
update_state(dev, &e);
}
dev->sync_state = SYNC_NONE;
}
/* FIXME: if the first event after syncing is a SYN_DROPPED, log this */
/* FIXME: if the first event after SYNC_IN_PROGRESS is a SYN_DROPPED, log this */
/* Always read in some more events. Best case this smoothes over a potential SYN_DROPPED,
worst case we don't read fast enough and end up with SYN_DROPPED anyway.
@ -573,7 +582,7 @@ int libevdev_next_event(struct libevdev *dev, unsigned int flags, struct input_e
}
if (flags & LIBEVDEV_FORCE_SYNC) {
dev->need_sync = 1;
dev->sync_state = SYNC_NEEDED;
rc = 1;
goto out;
}
@ -589,13 +598,15 @@ int libevdev_next_event(struct libevdev *dev, unsigned int flags, struct input_e
rc = 0;
if (ev->type == EV_SYN && ev->code == SYN_DROPPED) {
dev->need_sync = 1;
dev->sync_state = SYNC_NEEDED;
rc = 1;
}
if (flags & LIBEVDEV_READ_SYNC && dev->queue_nsync > 0) {
dev->queue_nsync--;
rc = 1;
if (dev->queue_nsync == 0)
dev->sync_state = SYNC_NONE;
}
out: