Re: [gentoo-user] Initial console messages garbled

["Sid Spry" <sid@aeam.us>]

> On Thu, Jun 25, 2020 at 2:55 AM Robin Atwood <robin@binro.org> wrote:
> >
> > On Wed, 24 Jun 2020 13:31:30 -0400
> > tedheadster <tedheadster@gmail.com> wrote:
> >
> > > Robin,
> > >  are you comfortable just going with a bare-bones console and build a
> > > new kernel where you _disable_ CONFIG_FB? That might do it.
> > >
> > > Alternately, you can hook up a serial cable to another computer and
> > > set "console=ttyS0,115200n8".
> >
> > I will try that, if it works it will at least give me a chance to look
> > at the error messages.
> >
> > I don't think I have any serial cables!
> >
> 

Well, you may need to buy a cable one way or another if your issue is very early in the boot process, typically qualified as "before the console comes up." Netconsole may help you though.

Most motherboards used to have potentially unpopulated serial port headers on them. Those seen to be disappearing.

The replacement is https://www.kernel.org/doc/html/v5.4/driver-api/usb/usb3-debug-port.html. Most (all?) desktop xHCI controllers support a device mode that is essentially a very high speed CBC ACM serial port. This is especially useful for debugging laptops.

You do need to either make or buy the special A to A cable.