Thanx for the fast reply, 
that helped me a lot, but I have one more question...

Does the glibc support async operations? I only saw support for 'non-blocking' 
operations which is something complete different here. Somethings which 
corresponds to struct OVERLAPPED of the Win32 API and the functions using it.

CU,
Jan

On Friday 21 March 2003 16:50, David Brownell wrote:
> Hi,
>
> > 1.
> > does anybody have any experience with async usb transfers? When I say
> > asynchronous transfers I refer to non-blocking (write/read/ioctl) calls
> > the user thread can test or wait for their completion.
> >
> > In the write/read/ioctl it is no problem to pass an urb down
> > asynchronously. But how do I test/wait for its success? If nobody has a
> > better idea, I would do that in ioctl with a special ioctl-code for
> > testing/waiting.
>
> Have the urb's completion callback set some flag (it'll be
> done in_interrupt, so lock appropriately); that's enough
> for the "test" part.
>
> If you use a "struct completion" then then have the callback
> issue complete(), then you can wait using wait_for_completion(),
> or maybe wait_event_interrupible(), and test with appropriate
> locking (the lock on the wait queue head inside that struct).
>
> > 2.
> > Does the host-controller driver queue urbs? Or do I have to wait for the
> > completion of an urb before I can pass the next one down?
>
> It queues bulk, though for UHCI you'll need to use USB_QUEUE_BULK
> in urb->transfer_flags.  It also queues ISO.
>
> On 2.5, all transfer types are transparently queued.
>
> - Dave
>
> > Thanx,
> > Jan
>
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