[PATCH synaptics] eventcomm: ensure we're on the same clock as the server

[Peter Hutterer]

Default on evdev devices is CLOCK_REALTIME. If that clock falls behind the
server's CLOCK_MONOTONIC, motion after a clickpad click may be delayed by the
difference in the clocks.

In detail:
When the timer func is triggered, GetTimeInMillis() which is CLOCK_MONOTONIC,
is stored as hwState->millis. The eventcomm backend uses struct
input_event time (CLOCK_REALTIME).

When we read events from the device, if the evdev time is less than the server
time, the fix for (#48777) sets the current event time to hwState->millis.
Until the evdev time overtakes that stored time, all events have the
hwState->millis time.

If during that time a clickpad triggers a physical click,
clickpad_click_millis is set to hwState->millis + the ignore-motion timeout.
Thus, all motion is ignored until the event time overtakes that stored
time.

The whole issue is further enhanced by us unconditionally setting the timer
func if we get any events, which is a separate issue anyway.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/eventcomm.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/eventcomm.c b/src/eventcomm.c
index 845f547..4a646af 100644
--- a/src/eventcomm.c
+++ b/src/eventcomm.c
@@ -39,6 +39,7 @@
 #include <dirent.h>
 #include <string.h>
 #include <stdio.h>
+#include <time.h>
 #include "synproto.h"
 #include "synapticsstr.h"
 #include <xf86.h>
@@ -88,6 +89,8 @@ struct eventcomm_proto_data {
 
     struct libevdev *evdev;
     enum libevdev_read_flag read_flag;
+
+    int have_monotonic_clock;
 };
 
 #ifdef HAVE_LIBEVDEV_DEVICE_LOG_FUNCS
@@ -234,6 +237,7 @@ EventDeviceOnHook(InputInfoPtr pInfo, SynapticsParameters * para)
     SynapticsPrivate *priv = (SynapticsPrivate *) pInfo->private;
     struct eventcomm_proto_data *proto_data =
         (struct eventcomm_proto_data *) priv->proto_data;
+    int ret;
 
     if (libevdev_get_fd(proto_data->evdev) != -1) {
         struct input_event ev;
@@ -253,7 +257,6 @@ EventDeviceOnHook(InputInfoPtr pInfo, SynapticsParameters * para)
 
     if (para->grab_event_device) {
         /* Try to grab the event device so that data don't leak to /dev/input/mice */
-        int ret;
 
         ret = libevdev_grab(proto_data->evdev, LIBEVDEV_GRAB);
         if (ret < 0) {
@@ -265,6 +268,9 @@ EventDeviceOnHook(InputInfoPtr pInfo, SynapticsParameters * para)
 
     proto_data->need_grab = FALSE;
 
+    ret = libevdev_set_clock_id(proto_data->evdev, CLOCK_MONOTONIC);
+    proto_data->have_monotonic_clock = (ret == 0);
+
     InitializeTouch(pInfo);
 
     return TRUE;
@@ -682,7 +688,10 @@ EventReadHwState(InputInfoPtr pInfo,
             switch (ev.code) {
             case SYN_REPORT:
                 hw->numFingers = count_fingers(pInfo, comm);
-                hw->millis = 1000 * ev.time.tv_sec + ev.time.tv_usec / 1000;
+                if (proto_data->have_monotonic_clock)
+                    hw->millis = 1000 * ev.time.tv_sec + ev.time.tv_usec / 1000;
+                else
+                    hw->millis = GetTimeInMillis();
                 SynapticsCopyHwState(hwRet, hw);
                 return TRUE;
             }
-- 
1.9.3