Hi! In the last thread about using FreeBSD's bootloader to bring UEFI support to our port, Chris said this:
> It has been a couple of years but I think FreeBSD contains some of the Intel > code to interface to UEFI and via this you can get to the UEFI console. This > should be easy but it comes with a side effect. > > UEFI boots in graphics mode and so it's console on a PC is a slow scroll one. > On > boards like a Minnow using the UEFI console has the advantage of being able to > support any redirection UEFI has enabled such as a serial port. The > disadvantage > of this is performance and overhead. In time this may be a boot option. > > What I am not sure is the boundary between UEFI and the kernel and what is > enabled or available when the kernel is loaded. Source: https://lists.rtems.org/pipermail/devel/2018-June/022136.html According to my understanding, the efi_console is not available to the kernel - only to the loader.efi (the PE image of the bootloader, which eventually loads the ELF kernel). (In brief, my reasoning for this belief is that efi_console is defined and initialized only through the bootloader code (in stand/efi/main.c, when cons_probe is called). The efi_console relies on UEFI's BootServices, which won't be accessible when the ELF kernel is loaded, because ExitBootServices() is called before loading the kernel (as part of bi_load).) Given that information, it makes more sense to actually port a console driver that the ELF kernel uses, not that the bootloader uses. I'll look into how FreeBSD implements their UART console (https://github.com/freebsd/freebsd/blob/1cfbfa1fae9926303f69532a97a5a766fa672582/sys/dev/uart/uart_tty.c), and look into possibly reusing RTEMS' existing drivers for UART (NS16550?) as applicable. I'm not sure I know enough about serial programming _yet_, so do let me know if you think you have any resources that would be useful or if you'd like to fine-tune my plan! P.S. - Since we last disussed it, the context initialization and switching are working, and the port does now make it to the user's Init task! :D Cheers _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
