sending zero length skb's

[Duncan Sands]

> > Are you sure that the skb is simply not sent?  If so, that's fine by me.
> > I got the impression that things got into a bit of a mess in that case.
> > Did you test it?
> 
> I didn't test it, but I think I can prove it: usbatm_write_cells(), when
> given a zero length skb, immediately returns zero due to the condition
> in the loop; usbatm_tx_process() then advances to the next skb.

Because of the test on ctrl->len?

        for (num_written = 0; num_written < avail_space && ctrl->len;

I missed that, sorry.  However, if this is this only skb then we will
then submit an urb with zero length.  I guess that's OK.

Ciao,

D.