USB console support "was: NetBSD-7.0 boots OK and NetBSD-8.0 hangs/crashes during boot on a MacBook7,1)

At Mon, 06 Jul 2020 13:13:03 -0700, "Greg A. Woods" <[email protected]> wrote:
Subject: Re: NetBSD-7.0 boots OK and NetBSD-8.0 hangs/crashes during boot on a MacBook7,1
>
> Or indeed any device with any kind of USB port, e.g. a laptop.

Oh, and I wanted to mention something else that I'd forgotten about but
stumbled across again the other day while debugging servers:

Xen supports writing console messages to a special kind of USB port:

	"console=dbgp" indicates that Xen should use a USB debug port.

http://xenbits.xenproject.org/docs/4.11-testing/misc/xen-command-line.html

There's more about it in this thread:

https://lists.xenproject.org/archives/html/xen-devel/2009-03/msg00436.html
https://lists.xenproject.org/archives/html/xen-devel/2009-03/msg00458.html


Further of interest is that Xen also supports writing to both a COM port
and the "vga" console simultaneously.  Indeed it may support writing to
"dbgp" at the same time as well.  This is something I looked into for
NetBSD/i386 some time ago, but never got it fully working.  To me I
think it would be super incredibly valuable for the boot code to be able
to talk to both a serial port and the "pc" console simultaneously.  It
is less important for the kernel to do so, but it still would be nice.

--
					Greg A. Woods <[email protected]>

Kelowna, BC     +1 250 762-7675           RoboHack <[email protected]>
Planix, Inc. <[email protected]>     Avoncote Farms <[email protected]>

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