flight: osd: properly display reset reason

[mlyle]

We immediately returned before which prevented it from working.

[tracernz]

Would prefer pos += len, or pos += AlarmString(... instead of len, and then write a null char at pos but I suppose this will do. :-P

[tracernz]

Looks good.

[dustin]

len won't ever be < 0, so it doesn't seem all that useful to have this condition here.

[mlyle]

Just in case it ever returns error in the future, I figured. This is my second variant of this..

[tracernz]

Looks like it will be 0 if there are no warning/error/critical alarms?

dRonin/flight/Libraries/alarms.c

Lines 329 to 396 in 080150a

	int32_t AlarmString(SystemAlarmsData *alarm, char *buf, size_t buflen, bool blink, uint8_t *state) {
	*state = SYSTEMALARMS_ALARM_OK;
	buf[0] = '\0';
	int pos = 0;
	// TODO(dustin): sort the alarms by severity. Alarm messages
	// will get truncated. We want the most urgent stuff to show
	// up first, having warnings show up only if there's space.
	for (int i = 0; i < SYSTEMALARMS_ALARM_NUMELEM; i++) {
	if (((alarm->Alarm[i] == SYSTEMALARMS_ALARM_WARNING) ||
	(alarm->Alarm[i] == SYSTEMALARMS_ALARM_ERROR) ||
	(alarm->Alarm[i] == SYSTEMALARMS_ALARM_CRITICAL))) {
	if (!alarm_names[i][0]) {
	// zero-length alarm names indicate the alarm is
	// explicitly ignored
	continue;
	}
	// Returned state is the worst state.
	if (alarm->Alarm[i] > *state) {
	*state = alarm->Alarm[i];
	}
	char current_msg[LONGEST_MESSAGE+1] = {0};
	switch (i) {
	case SYSTEMALARMS_ALARM_SYSTEMCONFIGURATION:
	strncpy(current_msg,
	(const char*)config_error_names[alarm->ConfigError],
	sizeof(*config_error_names));
	current_msg[sizeof(*config_error_names)] = '\0';
	break;
	case SYSTEMALARMS_ALARM_MANUALCONTROL:
	strncpy(current_msg,
	(const char*)manual_control_names[alarm->ManualControl],
	sizeof(*manual_control_names));
	current_msg[sizeof(*manual_control_names)] = '\0';
	break;
	default:
	strncpy(current_msg, (const char*)alarm_names[i], sizeof(*alarm_names));
	current_msg[sizeof(*alarm_names)] = '\0';
	}
	int this_len = strlen(current_msg);
	if (pos + this_len + 2 >= buflen) {
	break;
	}
	if ((alarm->Alarm[i] != SYSTEMALARMS_ALARM_WARNING) && !blink) {
	this_len += 1;
	while (this_len > 0) {
	buf[pos++] = ' ';
	this_len--;
	}
	continue;
	}
	memcpy(&buf[pos], current_msg, this_len);
	pos += this_len;
	buf[pos++] = ' ';
	}
	}
	buf[pos] = '\0';
	return pos;
	}

-e- derp, you are suggesting just unconditionally adding len. Fair comment.

[tracernz]

Looked over this pretty well. The existing code has potential for a future bug (#1120), but I'm happy this is safe for now.