Re: Hibernate after alarm wakes from STR

David Brownell
2007-07-09T16:26:32Z

On Monday 09 July 2007, Marcelo Tosatti wrote:
> On Sun, Jul 08, 2007 at 07:44:03PM -0700, David Brownell wrote:

> > Better a /sys/power/wakeup_event (or whatever) that's more easily
> > found. It could link to the device issuing the event.
>
> As you mentioned, there might be two wakeup sources (RTC and power
> button for instance) or even more at the same time.

Actually I though I said that there would be races. Though come
to think of it, one way they'd show up on a typical embedded system
would be to have multiple wake IRQs pending ... you couldn't tell
which one came first. (The typical case would be a single event,
of course.) ACPI-ish systems would do that with GPEs and the
magic "rtc woke" flag.

And then there are shared IRQ lines serving as wake sources. There
could be three wake-enabled devices on that line (plus others that
aren't wake-enabled); the drivers returning IRQ_HANDLED should likely
be reported as having been wake sources, but not the ones returning
IRQ_NONE ...

... so yes, systems might need to present multiple wake events.

> Do you think its fine to simply but the device separated by spaces in
> the wakeup_event file?
>
> Sounds fine by me, but what about the one-value-per-file sysfs rule?

Better to have that node be a directory of links then, rather than
a single link.

Note that I'm just throwing ideas out there. I suspect that
in the general case it may not be easy to map from wake event
to device, without infrastructure that's now missing.

- Dave