On Wed, 11 Jun 2025, Daniel P. Berrangé wrote:
On Wed, Jun 11, 2025 at 02:37:08AM +0200, BALATON Zoltan wrote:
On Tue, 10 Jun 2025, Bernhard Beschow wrote:
The next patch will make dtc mandatory for boards with a bundled DTB, causing
these boards to be omitted when dtc is missing. Allow packagers to force the
build of those boards by providing an option.
I don't like this. This might result in some machines missing from some
distros if they don't notice this and forget to update their packages and
these are machines I care about.
"Someone might not notice & screw up" is pretty much an argument for
not doing anything at all. We publish release notes to alert distros
More like "if it ain't broke don't fix it".
to these kind of changes which is a reasonable effort on our part.
Distros need to play their part by reading them and adapting to the
changes. They can also compare the available options with new and
old QEMU to identify any new build features they need to handle when
updating.
Also what guarantees that we don't get bugs
by compiling the device tree with different dtc versions which might
generate different binaries? The binaries we have now are known to work and
don't take much space so keeping them for convenience might be simpler. If
it worked so far why change it now?
Ultimately the DTC project has responsibility to not cause regressions
in new releases they issue, as is the case for any 3rd party dep that
we rely on.
We have CI jobs that can run on different distros. If we have coverage
of the boards in functional test suite that provides a way to validate the
operation with differing DTC versions as a sanity check.
Distributing pre-built binaries in source release tarballs is a long
standing issue with QEMU's releases. If we can eliminate the pre-bbuilt
DTB and only ship the source that is a good thing IMHO.
If this was using dtc from the submodule when not using system libfdt then
at least it would not result in dropped machines and we had a known working
dtc to compile with. Why isn't that used when we already have it for libfdt?
Are there any platforms that we target which still lack dtc ? The
submodule was there to plug gaps in distro support long ago, but
if every distro has dtc available the submodule is redundant.
OK, can we then make libfdt and dtc mandatory and not build at all instead
of disabling boards without it? I only care that my boards will be in
distro packages so users don't have to compile and I don't have to provide
binaries which would also be ensured if we require dtc, then the dtbs can
be dropped.
There's still a potential issue that some of the dts files are old and may
not compile with newer dtc and changing them may upset the guest but
hopefully we won't get that.
Regards,
BALATON Zoltan
