Hello,
for an embedded project I’m implementing a bootsplash application which should
as well display service names are starting.
This is based on kdbus and uses the sd-bus API to communicate with systemd (for
example boot process percentage property is polled).
Now I try to monitor the kdbus (system bus) to capture the events which
indicate that a service was started. (works very well for testing with "busctl
monitor“ tool).
I assumed that the method_call „StartUnit“ would be a good indicator, so I
tried to monitor for those messages by using following code (shortened and only
significant parts copied here):
-.-.-.-.-.-.-.-.-.-.-. schnipp -.-.-.-.-.-.-.-.-.-.-
r = sd_bus_open_system(&bus);
…
r = sd_bus_add_match(bus, NULL, "", do_something_callback, NULL); /* should
not filter anything, I expect it triggers on any message */
…
for (;;) {
sd_bus_message *m = NULL;
r = sd_bus_process(bus, &m);
if (r < 0) {
fprintf(stderr, "Failed to process bus: %s\n",
strerror(-r));
goto finish;
}
if (r > 0) /* we processed a request, try to process another
one, right-away */
continue;
/* Wait for the next request to process */
r = sd_bus_wait(bus, (uint64_t) -1);
if (r < 0) {
fprintf(stderr, "Failed to wait on bus: %s\n",
strerror(-r));
goto finish;
}
}
…
-.-.-.-.-.-.-.-.-.-.-. schnapp -.-.-.-.-.-.-.-.-.-.-
The interesting thing is that this code only sees „signal“ type messages - but
not any other like „method_call“.
I did extensive testing, tried different code variants, for example by
processing "sd_bus_message *m“ directly in the for loop with
„sd_bus_message_is_method_call“ - but the effect is the same I don’t get
„method_call“ as an event.
Is there any suggestion what could be the reason ? (is that generally the right
way what I try here to do ?)
Many thanks for any feedback which points me to the right direction
Kind Regards
Thomas Schmidt
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