> Oliver, I don't understand your point. Which devices and drivers are you
> referring to?
Scsi and drivers that drive scsi cards or their equivalent.
> "Provided that you know when you can safely autosuspend." If the driver
> doesn't know when it can suspend its device, who else would know?
Those who understand the semantics, which with scsi (sg) might be
in user space.
> "And provided you can restore the full state." Well yes, clearly, if
> suspending a device loses some state unavoidably then the driver should
> never autosuspend. Not unless someone tells it that it's okay to go ahead
> and lose the state.
>
> "I doubt you can with scsi because the driver doesn't understand the
> commands." Well, for example, usb-storage is a SCSI driver of sorts, and
> it certainly understands suspend/resume. (Or more accurately, it can be
> made to understand with a relatively small patch.) I'm not sure what the
> state of suspend/resume support is in drivers like sd or sr, but that
> shouldn't make much difference to usb-storage. It doesn't have to tell
> the SCSI layer when the USB transport is suspended. All it has to do is
> resume the USB connection when the next SCSI command comes along.
No. It has to guarantee that the device will react the same way to the next
command whether a suspension has intervened or not. I really doubt you
can do that for all devices going into power save.
Regards
Oliver
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