On Tuesday 08 February 2005 11:54 am, Andi Kleen wrote: > On Tue, Feb 08, 2005 at 11:48:11AM -0800, David Brownell wrote: > > On Tuesday 08 February 2005 11:05 am, Andi Kleen wrote: > > > My plan was to just drive a normal host2host cable through > > > debug port. It'll need some hacks, but should not be too bad. > > > > I'd have expected some of them to _be_ "debug devices" in fact, > > but I'm not sure how common that is. My extremely limited sample > > shows no success there ... they didn't have debug descriptors. > > Just debug port should work even without debug descriptors, > shouldn't it? (with some manual scanning of addresses)
Only in an rather error-prone mode where you just _assume_ any device hooked up to the debug port will talk to you. The debug port only supports 8 byte packets. Debug descriptors fit in just 4 bytes, so a debug port driver can easily check "is this a debug device?" and behave sanely no matter what the answer is. But to look at a device and see if it's a particular vendor's host2host cable requires reading not just bytes 0-7 of the device descriptor, but also bytes 8-13 ... a debug port driver can't do that. Likewise you'd have to assume you know the right configuration to set, and how its endpoints are set up. For debug devices, you just set "debug mode" instead of setting a config; the endpoints to use are part of the debug descriptor. - Dave ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
