[linux-pm] Some thoughts on suspend/resume development

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Hi!

> > This would be doing something like partial-tree suspends, but I'm not sure
> > if this is best done in the kernel or in userspace with a proper tool.
> 
> Hrm... I think it's more complex than that. We need 2 way communication
> between parents & childs. For example, if a parent is informed when a
> child entered an idle-suspend state (local dynamic PM), it can enter
> itself into some kind of suspend state when all it's offspring is in
> such a state (like USB bus suspend when devices are idle, Apple does
> that afaik, or did that in MacOS 9).
> 
> But that means child -> parent notifications
> 
> Also, states tend to be bus specific (PCI D states, USB states, ...)

Perhaps we should have more types like pci_power_t, then, and pass
those around? Whether notification needs to be sent up or down seems
bus-specific, too, so maybe it makes sense to do this per-bus?

> > > For user suspends (made through sysfs) the user may want to convey
> > > arbitrary information to a driver, things like which clocks to turn
> > > off, which power level to change to, and so on.  This information
> > > will vary from driver to driver, and the PM core shouldn't even try to
> > > impose any sort of structure on it.  I think the best approach will be
> > > to pass to the driver a character pointer giving the data written to
> > > /sys/.../power/state, so that users can send whatever they want just
> > > by writing it to the file.  This means adding an additional field to
> > > pm_message_t.
> > 
> > Uh, that would really suck. This would entail a string parser in every
> > driver, which is what we wanted to get away from with sysfs. A better way
> > would be to have a driver export a file with the specific features that it
> > supports encoded in a meaningful and efficient way (i.e. a fixed-length
> > string, character, or constant).
> > 
> 
> What aboout a new IRC meeting to discuss those things ?

Why not... But having it in European-friendly time would certainly
help.

								Pavel
-- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!

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