On Fri, Apr 19, 2019 at 09:54:35AM -0700, Alison Schofield wrote: > On Thu, Apr 18, 2019 at 05:07:12PM +0200, Rafael J. Wysocki wrote: > > On Thu, Apr 18, 2019 at 5:02 PM Keith Busch <keith.busch@xxxxxxxxx> wrote: > > > > > > On Wed, Apr 17, 2019 at 11:13:10AM -0700, Alison Schofield wrote: > > > > ACPI 6.3 changed the subtable "Memory Subsystem Address Range Structure" > > > > to "Memory Proximity Domain Attributes Structure". > > > > > > > > Updating and renaming of the structure was included in commit: > > > > ACPICA: ACPI 6.3: HMAT updates (9a8d961f1ef835b0d338fbe13da03cb424e87ae5) > > > > > > I was not really happy with that HMAT update. Platforms implementing > > > 6.2's HMAT continue to exist even if 6.3 isn't backward compatible. We > > > just lost the original subtable definition. > > > > Well, that's true, sadly, but the question is what to do in the kernel. > > > > Definitely, the 6.3 format needs to be supported, but if the 6.2 ships > > anywhere in practice, that will need to be supported too. > > So, what's the usual practice when ACPI tables are updated? > Do we define separate 6.2 and 6.3 versions of this subtable and let > the kernel figure out which one its looking at? Yeah, I think either new struct definitions for incompatible versions, or unions for conflicting members would be good. But I think Rafael is saying we only care if someone's shipping platform implements a particular version. I don't happen to know which ACPI version platforms I'm interested are going to release with, so I have HMAT supporting either right now. The 6.3 update wasn't difficult to handle this time.
