From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keith Busch Subject: Re: [PATCH] acpi/hmat: Update acpi_hmat_type enum with ACPI_HMAT_TYPE_PROXIMITY Date: Fri, 19 Apr 2019 11:09:59 -0600 Message-ID: <20190419170958.GA9331@localhost.localdomain> References: <20190417181310.27613-1-alison.schofield@intel.com> <20190418145640.GA7659@localhost.localdomain> <20190419165435.GA2284@alison-desk.jf.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190419165435.GA2284@alison-desk.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Alison Schofield Cc: "Rafael J. Wysocki" , "Rafael J. Wysocki" , Robert Moore , "Schmauss, Erik" , ACPI Devel Maling List , Linux Kernel Mailing List List-Id: linux-acpi@vger.kernel.org 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 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.