Date: Mon, 3 May 2004 17:32:06 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: John Birrell <jb@cimlogic.com.au> Cc: current@freebsd.org Subject: Re: USB isochronous transfers Message-ID: <Pine.BSF.4.21.0405031729390.40085-100000@InterJet.elischer.org> In-Reply-To: <20040504001029.GG58608@freebsd3.cimlogic.com.au>
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On Tue, 4 May 2004, John Birrell wrote: > Are there any USB experts here? > > The ugen driver in current has code that treats an isochronous endpoint > which has a wMaxPacketSize of zero as invalid and won't open it. > > I have a board here that reports it's isochronous endpoint like that. > > On page 47 of the USB Specification 2.0, I see this: > > "All device default interface settings must not include any isochronous > endpoints with non-zero data payload sizes (specified via wMaxPacketSize > in the endpoint descriptor). Alternate interface settings may specify > non-zero data payload sizes for isochronous operation." > > My board is supposed to be a reference implementation from Philips > for their 1581 USB chip and their MPEG2 chips. It only has the default > interface. I had a look in my USB book (The mindshare USB2 book) but it didn't illuminate the subject any more than what you have already found.. The whole concept of all those descriptors and how they all fit together is confusing at the best of times. > > The board seems to behave like the specification says it should. FreeBSD's > ugen implementation seems to be the odd one out. > > Does anyone know what to expect from a device with wMaxPacketSize = 0? > > -- > John Birrell > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >
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