On Mon, Sep 12, 2022 at 10:04:24PM +0200, Edgar Fuß wrote: > > If you can setup a serial console, it may make things much easier. > I do have a serial port on the machine. > > > I almost always use serial consoles on dev machines; I don't remember the > > details but doing the equivalent of a putchar very early was possible. > Is the BIOS still available or how does that work?
Basically it just requires a outb to the serial port's TX register (well, you also need to busy-wait for the transmit to complete, or characters will be lost). This is simple enough to have it working early in boot, as early as the consinit() call in init_x86_64(). I'm almost sure I used printf() in init_x86_64 with a serial console (but after the consinit() call or course). I definitively used it in pmap_bootstrap(). -- Manuel Bouyer <bou...@antioche.eu.org> NetBSD: 26 ans d'experience feront toujours la difference --