> "Daniel C. Sobral" wrote:
> > 
> > Mitsuru IWASAKI wrote:
> > >
> > >  - support S2, S3, S4 (hibernation) sleeping transition.  S4 sleep
> > >    require some hack in boot loader.... needs help.
> > 
> > I thought hibernation was entirely controlled by kernel? What do you
>                                                    ^^^^^^
> Err, BIOS.
> > need?

Yes, we need to consider both.  In ACPI spec. 1.0b 9.1.4 S4 Sleeping
State, this is described that S4 supports two entry mechanisms: OS
initiated and BIOS initiated.

From: Intel, Microsoft, Toshiba
Subject: Advanced Configuration and Power Interface Specification 1.0b
Date: Tue, 2 Feb 1999 07:55:24 +0900
> In the OS-initiated S4 sleeping state, the OS is responsible for
> saving all system context. Before entering the S4 state, the OS will
> save context of all memory. Upon awakening, the OS will then restore
> the system context.  When the OS re-enumerates buses coming out of the
> S4 sleeping state, it will discover any devices that have come and
> gone, and configure devices as they are turned on.

I think OS-initiated S4 (hibernation) in FreeBSD has enough advantages
because we can do `Save-to-Disk' anywhere even on non-laptop machines
which BIOS doesn't support hibernation.
FreeBSD supports crash dump facility here, so I'm expecting that
`Save-to-Disk' by kernel would not be so difficult. We might need
dedicated swap partition for OS-initiated S4 because used swap areas
need to be protected for the system oprerations after awakening.
The boot loader is the best place for restoring the system context in
FreeBSD I think.

Unfortunately I don't have enough knowledge on crash dump and boot
loader to implement OS-initiated S4 transition (actually, this is not
related with ACPI at all).
I love to see someone say `hey!  I'll take this one!' :-)


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