On Sat, 21 Jul 2007, Pavel Machek wrote:
So it will be break at least battery status and "AC plugged in"
status, because those are handled by ACPI and we do not know how to
control them by hand.
It seems that it should be possible to initialize ACPI as if the system
just booted up normally. Then battery status and such should be
correct, since they are correct after normal initialization.
It should be possible to make hibernate look just like a reboot to all
of the devices, including ACPI stuff.
Patch to make that work with swsusp/shutdown method would be indeed
welcome. It does not work today.
is this a problem in the restore path?
with the kexec approach (and ignoring suspend to ram and disk for the
moment) the system will actually get shutdown completely after the image
is written. on resume it gets cold booted. at this point the ACPI stuff
should have no problem
now if the ACPI drivers are storing something in ram about the battery
status and AC power status, but don't re-check after the resume, it
seems
That seems to be the problem. They store something in ram, and we
don't tell them that we resumed. That's why platform mode is
important, and way to go on ACPI systems.
this sounds like the few drivers that do this sort of thing (and this
should only be the things that report status, drivers that enable devices
should be taken care of) need a 'forget what you think you know, check the
reality of the hardware' function.
even without suspend I've sen these drivers get out of sync with reality,
and so such a function call would be useful to get them back in sync in
any case.
if such a 'check reality' function was available it should be
straightforward to call it after a non-ACPI hibrnate/resume
David Lang
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