Re: More serial ports in EFI bootstrap?

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

Emmanuel Dreyfus <manu%netbsd.org@localhost> wrote:
> On Fri, May 16, 2025 at 07:39:31AM +0000, Emmanuel Dreyfus wrote:
>> I have a Dell server with no serial port, and a serial console is highly
>> desirable for system administration. I wonder if EFI bootstrap could
>> be modified to use a serial port from a PCIe to serial card, or from a
>> USB to serial adapter.
>
> Replying to myself to tell some succes.
>
> The UEFI bootstrap uses UEFI for serial I/O, hence we need UEFI to 
> have a driver for the serial port in order to use it in NetBSD EFI
> bootstrap.

[snip]

> This is great, but the next step is booting the kernel. It does not
> support the console on the USB-to-serial adapter and I boot to 
> multiuser without a console.
>
> Hence the new question is: do we have any hope of using a USB-to-serial
> adapter for kernel console? I have not looked at it yet, but I understand
> there will be the issue that the USB-to-serial adapter cannot work 
> before a lot of devices initialization. It would be nice to have it 
> working for single-user mode, and that should be possible.

Do you want this to work before interrupts are enabled as well as after?