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

[Mike Frysinger]

On 07 Apr 2021 17:39, Luis Machado via Gdb-patches wrote:
> On 4/7/21 5:26 PM, Mike Frysinger wrote:
> > 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.
> 
> I'll take a look. Are you proposing we only use the prebuilt file from 
> the source tree instead of generating a new dtb file during the build? 
> And we should only do those things if maintainer mode is enabled?

if we're going to commit the prebuilt file to the tree, then yes, we should
only be using that.  we have a lot of similar styles:
* configure from configure.ac
* Makefile.in/aclocal.m4 from Makefile.am
* nltvals.def from common/gennltvals.py

so if maintainer mode is enabled, and dtc is available, and the dts is newer
than the dtb, we'd update the dtb in the source repo.  anyone changing the
dts would be responsible for this.  as you noted, this is pretty rare atm,
so shouldn't be a big deal.
-mike