Re: More serial ports in EFI bootstrap?

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

On Wed, Jun 04, 2025 at 01:27:39PM +0000, Emmanuel Dreyfus wrote:
> > Can (and should) we access the console via EFI interfaces in this case?
> 
> You can skip the call to UEFI ExitBootServices() but I guess you need
> to take care of not overwriting memory used by UEFI. I recall doing
> that to get console output later during kernel load process. It worked, 
> but I did not try to call UEFI Read/Write from the kernel.

No success. I have not been able to boot a kernel when skiping
ExitBootServices() in bootstrap, even if the kernel does not attempt
any UEFI I/O. The machine never reaches multi-user, and since there
is no console, I have no idea what happens.  The machine reboots
on its own after a while.

The behavior is the same with pc and com0 (over FTDI USB adapter)
console.

Another approach would be to use ucom0 as console once it is attached.
How feasible would it be to swap the console during kernel bootstrap?


-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost