[LinuxBIOS] USB Support

Peter Stuge stuge-linuxbios at cdy.org
Fri Jul 7 19:52:34 CEST 2006

This is a nice idea.

On Fri, Jul 07, 2006 at 04:18:25PM +0200, Stefan Reinauer wrote:
> > what you need is a debug device, which mostly looks like a usb
> > style null modem cable. No idea where to get this hardware
> > though.
> D'uh - it reads any usb 2 to usb 2 data link cable can be used for
> this purpose. Such cables are available for ~ 10$

Where did you read this?

I doubt they will work, unless the manufacturers were exceedingly
clever and actually implemented the DEBUG_MODE feature in the

I agree with your first observation that this will be a special
device, because of the DEBUG_MODE feature described in the spec as
well as the 8 byte limits on transfer size.

On Fri, Jul 07, 2006 at 09:21:57AM -0600, ollie wrote:
> What's on the other end of the cable? Just the usual USB port? What
> software we need (minicom)?

The spec only deals with the end of the debug device that connects to
the target system. I guess implementors are free to choose whatever
USB interface they wish to expose to the host ("remote" in the spec)
system as long as it has one max 8-byte bulk in endpoint and one max
8-byte bulk out endpoint.

I'm not sure if this requirement is compatible with the CDC spec that
USB-serial adapters implement, but it would indeed be very handy if
minicom+the kernel USB-serial driver could be used with the host end
of the debug device.

It's quite possible that the device requires a special application,
but in any case such an application would be trivial to hack up.
I think the hard part is to find or make the hardware. Or maybe not
so hard if you have a proven USB2 HS platform and are comfortable
with tweaking USB descriptors. All I have handy is USB2 FS. :(


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