RE: Potential problem with reading data from usb devices with ugen(4)

["Terry Moore" <tmm%mcci.com@localhost>]

Not only legitimate, but required, depending on the class protocol.

Best regards,
--Terry

> -----Original Message-----
> From: tech-kern-owner%NetBSD.org@localhost [mailto:tech-kern-owner%NetBSD.org@localhost] On
> Behalf Of Greg Troxel
> Sent: Wednesday, December 30, 2015 17:36
> To: Brian Buhrow <buhrow%nfbcal.org@localhost>
> Cc: Nick Hudson <nick.hudson%gmx.co.uk@localhost>; Nick Hudson <skrll%NetBSD.org@localhost>;
> tech-kern%NetBSD.org@localhost
> Subject: Re: Potential problem with reading data from usb devices with
> ugen(4)
> 
> 
> Brian Buhrow <buhrow%nfbcal.org@localhost> writes:
> 
> > 	To answer your question about whether there is a standard for
> > generating these packets, it seems there is not.  Linux expects you to
> > use an ioctl() to generate the packet while FreeBSD expects you to
> > send a write request with 0 bytes, as we do with the ugen(4) changes I'm
> making.
> 
> I meant: in the USB specification, is it legitimate to do zero-length
> transfer?