On Tue, 14 Dec 2021 10:30:26 +0000, Vladimir Oltean <vladimir.oltean@xxxxxxx> wrote: > > On Tue, Dec 14, 2021 at 10:20:36AM +0000, Marc Zyngier wrote: > > 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. > > That's an honorable set of guiding principles, but how do you apply them > here? Reverting Rob's change won't fix the past, and updating the code > to account for one format will break the other. As for trying one > format, and if there's an error try the other, there may be situations > in which you accept invalid input as valid. maz@hot-poop:~/arm-platforms$ git describe --contains 869f0ec048dc --match=v\* v5.16-rc1~125^2~19^2~16 This patch landed in -rc1, and isn't part of any release. Just revert it, and no damage is done. M. -- Without deviation from the norm, progress is not possible.
