Re: [linux-usb-devel] Re: hotplugging to deal with firmware download

[Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de>]

> > I agree. But usbcore should help as far as possible.
>
> What were you thinking would transform the "device model" level
> suspend/resume calls into USB level ones?  :)

OK, but where do we handle the case where resumption is impossible
because the device has been unplugged ?

> >>For example, suspending a bus-powered hub would need to morph into
> >>disconnecting the devices it could no longer power ... and in your
> >>case, suspending a network device that discards its firmware would
> >>also need to morph into a disconnect.
> >
> > That's exactly what you must _not_ do, you need to retain the information
> > which devices was on which port to resume correctly.
>
> Why would that be?  In those cases, the device MUST re-enumerate from
> scratch, there will be no USB state to resume.  In those cases the
> devices can't suspend; they can only disconnect/reconnect.
>
> And it'd be pointless, since if any device driver wants to save
> information about devices across reconnects -- like usb-storage does
> today -- it has all the tools it needs to do that already.  There's
> no need to bloat the core with such stuff.

That is not the entire truth.
The hub will be told to resume first. If we than scan the physical bus
and initiate initialisation of the devices found, there'll be chaos
once the "driverfs" layer tells devices to resume.

> Given that userspace tools can already be used to make network device
> names be pseudo-stable ("eth2" is always the one with address NN), and
> network drivers can even request specific names ("eth3") I don't see
> any reason any network device driver should want such functionality.

How about keeping up connections ?
The point of suspend/resume cycles is that the system is restored
to the state it had. IP, mac, filtering etc... must be restored, not only names.
In fact, if we have persistent names we don't need to care about names.

	Regards
		Oliver


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