On Tue, 14 Dec 2021 09:58:54 +0000, Vladimir Oltean <vladimir.oltean@xxxxxxx> wrote: > > Hi Marc (with a c), > > I wish the firmware for these SoCs was smart enough to be compatible > with the bindings that are in the kernel and provide a blob that the > kernel could actually use. Some work has been started there and this is > work in progress. True, I don't know what other OF-based firmware some > other customers may use, but I trust it isn't a lot more advanced than > what U-Boot currently has :) > > Also, the machines may have been in the wild for years, but the > ls-extirq driver was added in November 2019. So not with the > introduction of the SoC device trees themselves. That isn't so long ago. > > As for compatibility between old kernel and new DT: I guess you'll hear > various opinions on this one. > https://www.spinics.net/lists/linux-mips/msg07778.html > > | > Are we okay with the new device tree blobs breaking the old kernel? > | > | From my point of view, newer device trees are not required to work on > | older kernel, this would impose an unreasonable limitation and the use > | case is very limited. My views are on the opposite side. DT is an ABI, full stop. If you change something, you *must* guarantee forward *and* backward compatibility. That's because: - you don't control how updatable the firmware is - people may need to revert to other versions of the kernel because the new one is broken - there are plenty of DT users beyond Linux, and we are not creating bindings for Linux only. You may disagree with this, but for the subsystems I maintain, this is the rule I intent to stick to. M. -- Without deviation from the norm, progress is not possible.
