Am Montag, 28. Juni 2004 19:11 schrieb David Brownell:
> Oliver Neukum wrote:
>
> > That state of affairs is unsatisfactory. It means that the deeper suspension
> > modes lose a lot of their usefulness. Ideally the system after resumption is
> > just like at suspension (minus system clock). It seems to me that to reach
> > that goal you must never call disconnect() unless the device is physically
> > removed.
>
> That doesn't make sense for USB, which at its fundamental level
> doesn't distinguish "loss of VBUS power" from "physical disconnect".
> Devices that lose VBUS _will_ completely reset, and need to be
> re-initialized from scratch.
Yes, but why would it be impossible to restore the state the device had
before the suspension? And equally important, why do we need to treat
a physical reinitialisation like a logical disconnect()/probe()
The more logical model would seem to be an extreme form of resetting
a device. It retains more function.
> The very deep suspend modes can indeed have serious limitations,
> which come from trading off that "just like at suspension" state
> against saving more power.
We should seek to limit the limitations.
The only absolute limitation I see is not large
- you cannot do remote wake up
- you cannot detect pluggings during such suspension
- you cannot resume devices which have state unknown to the driver (sg etc.)
Regards
Oliver
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