Re: [linux-usb-devel] [RFC][PATCH 0/2] x86_64 Early usb debug port support.

[David Brownell <david-b@pacbell.net>]

On Wednesday 06 December 2006 1:24 pm, Andi Kleen wrote:
> >   - Host, to which that console connects (through the debug device);
> >     runs usb_debug, much like any other usb-serial device
> 
> My understanding was that the client could run in user 
> space only on top of libusb.

I suppose it could, if you didn't want to use it like a normal
serial consoe.


> > It's analagous to debugging an embedded box using a serial console
> > with a Linux host ... except the target here is a PC, not an ARM
> > (or PPC, MIPS, etc) custom board.
> > 
> > 
> > Once the coexistence issues between the debug port and normal EHCI
> > driver get worked, there's no reason not to keep using that debug
> > port as a system console.  
> 
> One reason is the one I covered in my last mail -- locking of the PCI
> type 1 ports.

That'd be part of coexistence.  The debug port is _designed_ to share
two different drivers like that ... EHCI can see, as it comes up,
whether the debug port is in use, and could then ignore it.  (At least,
unless/until the debug device gets removed.)

- Dave