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

[David Brownell <david-b@pacbell.net>]

Oliver Neukum wrote:
> Am Mittwoch, 5. Juni 2002 16:54 schrieb David Brownell:
> 
>>>>>OK, but where do we handle the case where resumption is impossible
>>>>>because the device has been unplugged ?
>>>>
>>>>If that's not already handled, it'd be a bug in the hub driver.
>>>
>>>Well, how will we handle it with respect to the resume function ?
>>>Do we report failure if there's no longer a device at the physical
>>>location ? IMHO we do.
>>
>>Report it to what?  And in what sense would it ever be an "error"
>>to remove a device -- even during suspend?
>
> The genric layer that did request the resumption must be told
> that this was impossible and the device should be purged.

Last time I did suspend/resume of a system with USB, the hub
driver _already_ handled that.  Presumably it still does.


>>>Now I am puzzeled. There must be some misunderstanding.
>>>Could you please outline, how we deal with a resumption
>>>if the devices lost power under the new scheme ?
>>
>>By definition, this is "(re)enumeration", not resumption.
>
> But how is the state restored ?

I seem to recall pointing you at usb-storage once already,
as the only USB driver today which needs to do such stuff.
It has a notion of device identity, based ISTR on serial
numbers, and saves that state. UTSL.

- Dave



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