Am Montag, 5. März 2007 20:45 schrieb Alan Stern:
> On Fri, 2 Mar 2007, Oliver Neukum wrote:
>
> > Have a delay attribute per interface and give each device an attribute
> > "SuspensionState" with the permissible values "on", "auto" & "suspend"
> > Handle RemoteWakeup as an orthogonal issue.
>
> After some more thinking...
>
> As you say, remote wakeup is an orthogonal issue. So if remote wakeup is
> enabled when the user writes "suspend" to the attribute, the device will
> wakeup when an external event occurs. If not, it won't.
OK, so we have two attributes "CanDoRemoteWakeup" and "WantRemoteWakeup"
The former is ro and comes from the descriptor, the latter is read/write.
!(CanDoRemoteWakeup && WantRemoteWakeup) -> no autosuspend
> This makes me doubt that we should prevent the device from waking up when
> an internal I/O request occurs. If the user really wants to prevent the
> device from waking up, then he should prevent I/O requests. The means for
> doing this will depend on the individual device.
Provided the user is capable of preventing that. I don't think we can
consider this self-evident.
> For example, consider a USB flash card reader. HAL normally probes these
> devices 4 times/second, checking to see whether a card has been inserted.
> This activity would prevent the device from staying suspended very long.
> However, if the user would suspend the underlying sd device then the
> requests from HAL would be stopped at the source.
>
> As another example, consider a USB network interface. Doing "ifconfig
> down" would prevent new requests from arriving.
And it would kill existing sessions. Maybe that issue should be left to
the drivers.
Regards
Oliver
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