Re: Boot console on PCI com port?

[David Laight <david%l8s.co.uk@localhost>]

On Tue, Oct 25, 2011 at 11:21:24PM +0000, John Klos wrote:
> Hi,
> 
> Is it possible to use a serial port on a PCI card as the boot console? I 
> know that there's little chance of using it if it can't be seen by the 
> BIOS, but on the other hand is there some magic way to get the kernel to 
> use it instead of the default video console?

It should be possible to build a kernel where the device mappings
put the console onto a pci card.
First thing is to work out where the serial port is usually mapped.
I've just looked at the GENERIC config, look at CONSDEVNAME.

If the card's serial port is a standard uart (16550 etc) it might
even be possible to get the boot code to use it.

You'll need to know the IO address (and assume it won't change)
then build the mbr code with COM_PORT=<io address> and COM_BAUD
set to the required baud rate.
(It is possible that the bios will add it into the serial port
table at 40:0)

The bootxx code might also need to be told the serial port info.
That is patchable by installboot.

        David

-- 
David Laight: david%l8s.co.uk@localhost