Date: Tue, 4 May 2004 10:10:29 +1000 From: John Birrell <jb@cimlogic.com.au> To: current@freebsd.org Subject: USB isochronous transfers Message-ID: <20040504001029.GG58608@freebsd3.cimlogic.com.au>
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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. 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
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