Re: Porting to my custom 030 board

> On Oct 1, 2025, at 3:59=E2=80=AFAM, Lawrence Manning =
<[email protected]> wrote:
>=20
> Hi Chris,
>=20
> Thanks for the mail and your interest in my board, and desire to get
> NetBSD working on it. I've had a very brief look at 11 but still can't
> really figure out how to begin my own porting effort. Do you have a
> set of changes which just add support for a new machine? Ideally
> something m68k, but I might glean some knowledge looking at another
> machine type.
>=20
> FWIW my offer is still open, but I can gather from the lack of
> interest that either not enough skilled people are interested in such
> a board, or that they know it would be a reasonable amount of work
> even for them?

Not a lack of interest on my part, certainly (just had other life stuff =
going on and it=E2=80=99s not always easy to have time for hobbies).  =
I=E2=80=99m also working on a home-brew 68030 system (the board design =
is basically done; I=E2=80=99m still working on test cases for all of =
the Verilog for the 3 CPLDs on the board).

I=E2=80=99ve been involved with the m68k ports in NetBSD since the =
early-90s, and I will be the first to admit that it=E2=80=99s a bit of a =
mess in terms of =E2=80=9Chow much code is duplicated=E2=80=9D.  I=E2=80=99=
ve been working on that, slowly, over the years.  The arc of the =
universe, etc. etc. etc.

Almost 2 years ago, as a fun project over the Christmas holiday, I did =
the =E2=80=9Cvirt68k=E2=80=9D port.  I don=E2=80=99t recall exactly how =
long it took me, but I=E2=80=99m pretty sure it was less than 2 weeks.  =
Sure, it=E2=80=99s a =E2=80=9Cvirt=E2=80=9D port, but it=E2=80=99s a =
pretty decent example.  It clearly shows machine-specific attachments to =
generic drivers.

For my own home-brew machine, I decided to take a step back and examine =
the landscape.  There are a fair number of 68030 home-brew systems out =
there in the wild, and so for my own machine I decided to try and make =
it easier for others to port NetBSD to their boards.  My plan is to use =
Flattened Device Tree, like NetBSD=E2=80=99s ARM SoC ports use.  This =
will make is SUPER easy to support additional home-brew machine with =
very few code changes because the device tree describes the hardware in =
a generic way, and the hardware that home-brewers use is all fairly =
common.  In my case, my system=E2=80=99s firmware has the device tree =
compiled in to the ROM, and it passes a pointer to it to the kernel =
using the standard m68k ABI.  But it=E2=80=99s not necessary to do it =
that way; it=E2=80=99s also possible to embed the device tree into a =
kernel binary or some auxiliary loader.  There are plenty of options.

Anyway, I=E2=80=99d suggest you poke around in sys/arch/virt68k as a =
starting point to get a feel for how a light-weight m68k port is put =
together.  I=E2=80=99m happy to answer any specific questions you have, =
and happy to discuss your board in more detail!

-- thorpej