Re: Console on USB

[Pete Zaitcev <zaitcev@redhat.com>]

> Date: Tue, 19 Aug 2003 21:58:45 -0700 (PDT)
> From: "Randy.Dunlap" <rddunlap@osdl.org>

> >> Is there any advice I might be able to use to get this going?
> >
> > You'd have to write it. Grep for register_console for starters.
> 
> usb/serial/console.c:255:         register_console(&usbcons);

Eeek, eating a crow now.

> >>  I really want to be able to catch some oops output.
> >
> > If oops happens with interrupts closed, forget about it.
> > USB needs interrupts to work. This is one of the reasons nobody
> > bothered to implement console over USB serial.
> 
> The call to register_console() also happens very late in the boot
> sequence, so if your oops is early, USB console won't help.

It's true for many consoles, that's why sparc allows
"-p" in SILO options, for instance. I think either wli or willy
did "early VGA printk" patch.

Interrupts are a major problem. Also, the USB stack is pretty
thick.

-- Pete