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OPAL_RTC_READ
-------------
Read the Real Time Clock.
Parameters:
uint32_t* year_month_day
uint64_t* hour_minute_second_millisecond
Calling:
Since RTC calls can be pretty slow, OPAL_RTC_READ is likely to first return
OPAL_BUSY_EVENT, requiring the caller to wait until the OPAL_EVENT_RTC event
has been signaled. Once the event has been signalled, a subsequent
OPAL_RTC_READ call will retreive the time. Since the OPAL_EVENT_RTC event is
used for both reading and writing the RTC, callers must be able to handle
the event being signalled for a concurrent in flight OPAL_RTC_WRITE rather
than this read request.
The following code is one way to correctly issue and then wait for a response:
int rc = OPAL_BUSY_EVENT;
while (rc == OPAL_BUSY_EVENT) {
rc = opal_rtc_read(&y_m_d, &h_m_s_ms);
if (rc == OPAL_BUSY_EVENT)
opal_poll_events(NULL);
}
Although as of writing all OPAL_RTC_READ backends are asynchronous, there is
no requirement for them to be - it is valid for OPAL_RTC_READ to immediately
return the retreived value rather than OPAL_BUSY_EVENT.
TODO: describe/document format of arguments.
Return codes:
OPAL_SUCCESS:
- parameters now contain the current time, or one read from cache.
OPAL_HARDWARE:
- error in retrieving the time. May be transient error,
may be permanent.
OPAL_PARAMETER:
- year_month_day or hour_minute_second_millisecond parameters are NULL
OPAL_INTERNAL_ERROR:
- something went wrong, Possibly reported in error log.
OPAL_BUSY_EVENT:
- request is in flight
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