[PATCH] [sim,moxie] Fix DTB generation mechanism and build failure

[Mike Frysinger]

On 07 Apr 2021 16:39, Luis Machado via Gdb-patches wrote:
> I ran into a build failure with --enable-targets=all due to the fact that
> the moxie sim expects to be able to use the dtc tool.  If it isn't available,
> the builds fails.
> 
> Given the device tree compiler (dtc) is not available everywhere, it seems
> fair to only generate the DTB file on the spot if we have such a tool.  For
> those who don't have the tool available, we can use a prebuilt version of the
> DTB available in the repository.

i think i asked about vendoring the tool in, but i think people were
(understandably) not super keen on the idea since it's not GPL or GNU.

> The DTS file hasn't changed since ~2009, so it seems pretty safe to assume
> a prebuilt version is suitable to be used.

and because it's quite small.  if it were much larger, i don't think we'd
want to do it this way.

> I also checked that the DTB file generated on an x86_64-Linux machine is the
> the same as the one generated on an AArch64-Linux machine.

right, by design, it should be stable no matter where it's created.

> Tested by running make/make install with/without the dtc tool.

i think we want to fold this under the existing maintainer logic.  check out
commit 8c379db285f2ab8ad298288e86103548b90674a2 for a bit more detail.  we'd
want to only update+install the version in the source tree rather than switch
between the one in the srcdir & the builddir one.

also look at how move-if-change is used in common/Make-common.in.

lmk if that's too vague :).
-mike