> > We want only one method of URB allocation, don't we?
>
> Of course. But that method could be used either to pre-allocate URBs and
> buffers like Matt is suggesting, or to allocate them on demand like we do
> now.
If we want to avoid the memory allocation in block io path problem,
we have to preallocate. Besides, it is faster.
> > > I'm puzzled how pre-allocation would help usb_kill_urb().
> >
> > Reentrancy. The URB can be resubmitted from the completion handler, but
> > it cannot have completed.
>
> I don't see what this has to do with pre-allocating URBs. (Also I don't
> understand what you mean "it cannot have completed", but maybe that's not
> important for this discussion.)
An URB with its buffer preallocated is bound to a device, respectively
an endpoint, so it cannot complete without triggering the same irq the
completion handler is running in.
Regards
Oliver
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