Re: [linux-pm] [PATCH 3/6] [-mm]: ACPI: duplicate ACPI sleep "alarm" attribute in sysfs

David Brownell
2007-01-08T20:39:08Z

> > 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.
>
> Isn't useful in what way? It'd be helpful for userspace to know that now
> that we're actually using S4 for swsusp, but I understand that it might
> not fit into the current API terribly well.

In that current API there's no way to tell anything at all about the
target system state inside a driver's suspend() method. So if there
were some characteristic of S4 (or S3 etc) that mattered to the driver
(it should test for the attribute, not S4/etc since S4 is ACPI-specific)
the driver couldn't do anything about it ... so as I said, not useful.

- Dave