On Tue, 2008-02-26 at 11:04 -0500, Alan Stern wrote:
> Please use Reply-To-All so that the mailing list can see your
> responses.
Sorry, didn't notice my dirty laundry was being aired in public...
*blush*
> On Tue, 26 Feb 2008, Jan Gutter wrote:
>
> > On Mon, 2008-02-25 at 11:10 -0500, Alan Stern wrote:
> >
> > > You can try adding an explicit delay to see if it helps. In
> > > drivers/usb/core/hub.c:hub_port_init(), add a call to msleep just
> > > before the line:
> > >
> > > for (i = 0; i < GET_DESCRIPTOR_TRIES; (++i, msleep(100))) {
> > >
> >
> > Ok, in desperation I tried 5000ms, and it worked. 2000ms is still not
> > enough though. I'm "bisecting" the time now to try to find out what the
> > minimum time is.
2000ms fails, but 3000ms succeeds. Keep in mind, though, that I did not
suffer any of these problems in 2.6.23. How the heck did it manage to
work there? Hub not shutting down for powersave, other init mechanism,
something like that?
> Maybe we should add some sort of exponential backoff to the delay time
> between the reset and the first Get-Descriptor request.
Hmmm, it would be interesting to chart the state diagram and cater for
all the broken hardware. I'm worried that this would cause some *other*
broken things to break in new and interesting ways...
> Still, if a device takes more than 2 seconds to initialize itself
> after a reset, what do you expect? According to the USB spec, it
> shouldn't take more than 10 ms.
I agree, but again, 2.6.23 == fun, 2.6.24 == no fun. Windows XP and
Vista (yeah right!) have no problems either. Even a single-chip DVD
player with USB-in has no problem (dunno if it uses USB2 or USB1.1,
though). Counterargument: this seems to be the only USB-device
regression in 2.6.24, if it were some weird timing issue in the USB
stack, the fallout *should* have been easily visible!
You think it's time to work on an instrumented 2.6.23 and compare the
code paths taken to those in 2.6.24?
Jan
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