Re: Grub2 UEFI boot and serial console output

[Andrei Borzenkov]

11.01.2017 16:27, Matwey V. Kornilov пишет:
> Hello,
> 
> What is the proper way to output GRUB2 menu to serial rs232 console when
> UEFI boot is used? I've copy-pasted GRUB_SERIAL_COMMAND="serial --unit=0
> --speed=115200" from Google because I didn't find anything else. It
> doesn't work.
> Now, reading grub sources, I see that the proper way should probably be
> something like GRUB_SERIAL_COMMAND="serial efi0".
> 

This is platform dependent. --unit=0 refers to COM1 on PC BIOS platform.
On EFI grub is using EFI Serial I/O Protocol and enumerates all handles
with this protocol using efiXX names. Then there is USB serial driver,
ARC and IEEE1275 where names are provided by firmware etc.

> Could you please point me to proper documentation?
> 

You are welcome to contribute to it. Adding template section for
platform dependent serial information and filling it with information
known so far will be excellent - then other may extend it.