Subject: Re: Hardware Console Redirection
To: Brian A. Seklecki <firstname.lastname@example.org>
From: Andrew Reilly <email@example.com>
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
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