Subject: Re: Hardware Console Redirection
To: Brian A. Seklecki <>
From: Andrew Reilly <>
List: netbsd-users
Date: 11/01/2006 13:59:04
On Tue, Oct 31, 2006 at 06:18:22PM -0500, Brian A. Seklecki wrote:
> I have noticed that the "Phoenix BIOS" console redirection feature on both 
> discontinues to operate once the kernel has booted (however, the 1st/2nd 
> stage boot loaders work fine).

Why is that a problem?  The BIOS doesn't use the console once
the kernel has booted.

> The advantage of native, hardware level BIOS -> VGA emulated console 
> redirection is that, much like Sun/MacPPC or any OPF/PROM aware platform 
> (Soekris), the OS/Bootblocks need not be aware of the serial console 
> semantics; -- only of a benign VGA console.

What serial console semantics do the bootblocks get wrong?

> Is there some routine in the *BSD kernel console code that performs an 
> operation, perhaps a reset, on the serial ports, that wouldn't happen in 
> DOS?

What sort of reset do you need?  I don't really understand the
question, I'm afraid.  Do you mean a hardware reset of the
serial port, or using the serial port to have the effect of
Ctl-Alt-Delete (NMI) from a PC keyboard?

> In the case of the Axiom device, the console is redirected to the BIOS 
> level "com0" 0x3f8.  In the case of the PowerEdge, the redirection is to a 
> "virtual com1" which is attached to the DRAC5 LOM card.
> I tried the FreeBSD loader(8) hint.sio.1.flags="0x40" to attempt to have 
> the kernel ignore the device without success.

You can build a kernel that explicitly doesn't have a driver
that will look at a particular serial port, I think (by making
it explicit which ports it *does* look at), but I don't
understand how that would help: you'd have a serial port that
would be used by the BIOS, but would do nothing once the main OS
was booted.