On Saturday 06 January 2007 9:57 pm, Matthew Garrett wrote: > On Sat, Jan 06, 2007 at 02:42:22PM -0800, David Brownell wrote: > > On Saturday 06 January 2007 3:35 am, Zhang Rui wrote: > > > > > > Create /sys/power/alarm. > > > > Urg. This doesn't work with the RTC framework, which accepts the reality > > that some systems have multiple RTCs ... /sys/class/rtc/rtcN/alarm is a > > much more appropriate location for that RTC's alarm. > > Especially since /proc/acpi/alarm is just banging on the RTC registers > - the only ACPI thing about it is that the FADT can expose whether or > not the extended registers exist, and then making sure that the GPE is > enabled. The FADT also exposes whether the RTC can wake from S4. You may have noticed that my rtc-cmos patch #3 exported the relevant FADT info to the RTC device using platform_data, but the S4 wake capability flag isn't useful for anything on today's Linux. Not speaking as an ACPI expert, I do see the ACPI spec says (right under fig 4-11 in my version) that RTC events don't require GPEs. Conceptually, one would expect that enable_irq_wake(RTC_IRQ) would set PM1.RTC_EN, and disable_irq_wake(RTC_IRQ) would clear it, on ACPI systems. It doesn't do that, though. But I did notice there was a lot of event infrastructure behind the /proc/acpi/alarm thing ... which I never observed to fire. Maybe it would be needed on systems with different RTC implementations... - Dave
