USB problem - how to disable an umass device?
olli at lurza.secnetix.de
Wed Mar 7 18:16:02 UTC 2007
Ivan Voras wrote:
> Oliver Fromme wrote:
> > Of course, a better way to solve the problem would be to
> > find out _why_ it is hanging in the first place. :-)
> > The first step would be to enter the kernel debugger and
> > take a stack trace, in order to find out where it is stuck.
> > It might be a good idea to take this issue to the freebsd-
> > usb mailing list.
> Actually, it resolved to be a very large timeout, on the order of
> 5 minutes per step, before something gives up and the boot process
That sounds like a bug where a loop counter isn't initialized
correctly, so a loop wraps around and has to go through the
whole range of a 32 bit int until it terminates, i.e. 2^32
which is 4 billion interations. Depending on what the loop
actually contains, that could very well take 5 minutes.
There have been bugs like that in the past.
If you enter the Debugger during the hang and print a stack
trace, you should be able to see where that loop is. Maybe
it's easy to spot the incorrect loop counter and fix it.
> > > I tried using loader hint hint.usb.2.disabled="1" but it doesn't
> > > work.
> > Unfortunately, hints cannot be used to disable devices in
> > general (which would be a desirable feature). That only
> > works for legacy devices (i.e. ISA) and some others.
> I'd argue that this is actually a bad thing - I'm sure there are
> situations where it would be useful to disable (almost) arbitrary
> nodes in the device tree, even down to specific pci busses.
Yes, that's what I mean. I'm sure it could be useful.
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
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