On Tue, 21 Sep 2004, David Brownell wrote:

> But I don't have to adopt that bogus terminology.  Which is why
> I said "bus suspend", which is clear and unambiguous; and makes
> sense outside of USB.  And best, it also keeps a foul taste out
> of my mouth.  ;)

All right.  From now on, whenever I'm talking to you I'll use "USB bus
suspend" in place of "USB global suspend".  :-)


> > I'm not talking about resubmission; I'm talking about existing URBs that 
> > were submitted before the interface/device was suspended.  These don't 
> > have to come from a driver, by the way -- they could come through sysfs or 
> > usbfs.
> 
> Those cases exist too; I certainly call "usbfs" a driver, and sysfs isn't
> unlike it.  But I think I missed the reason(s) you think this is ungood.

> Why should that be a problem?  Other than more squirrelly cases for
> HCDs to cope with, that is.  If everything suspends before the URBs
> time out, what would be the problem?

It's ungood because of the difficulty in unlinking an URB when the HC
isn't running.  At least some of the HCDs are interrupt-driven, and if
those interrupts don't arrive (because the hardware is stopped) unlinks
won't complete.

I was going to say that fixing this in the core would be easier than 
handling it in the HCDs.  But now I'm not so sure...  Maybe it would be 
just as easy for an HCD to unlink all its active URBs at the start of a 
suspend as it would be for the core to do it.

> Root hubs have some funky paths to "resbmit" through the timer
> though ...

You mean the status URB?  That isn't submitted through the timer; the 
timer just calls the HCD's hub_status() routine.  Actual [re-]submission 
occurs in [hub_irq() and] hub_activate().

Alan Stern



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