Which is why I was puzzled that you didn't start out doing it
the "right" way ... even just hard-wiring the dubious assumption
that "rtc0" is the right RTC to use. :)
Well, "rtc which (a) has an alarm, (b) may be used for system wakeup".
Assuming there *is* such an RTC ... fortunately, there will usually be
one on systems that are designed to go to sleep.
Easy enough. Given an RTC device node, you can tell whether it has
no chance at all to meet those requirements:
static int has_wakealarm(struct device *dev, void *name_ptr)
{
struct rtc_device *rtc = to_rtc_device(dev);
/* (a) has an alarm */
if (!rtc->op->set_alarm)
return 0;
/* (b) may be used for system wakeup */
if (device_may_wakeup(dev->parent))
return 0;
*(char **)name_ptr = rtc->name;
return 1;
}
Then there's a new class interface you may not have known about,
since it's been merged barely over a week now. You can use it
to find the name of the rtc to pass to rtc_open():
static char *find_wake_rtc(void)
{
char *pony = NULL;
dev = class_find_device(rtc_class, &rtc, has_wakealarm);
return pony;
}
On most PCs that will return the name "rtc0" ... and it'll do
the same on most of the other systems I have. On both of the
two-RTC systems I have that will return "rtc1". On systems
with no wakealarm-enabled RTC, that will return NULL.
Voila!
- Dave
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