On Thu, May 19, 2022 at 05:32:35PM +0200, Andrew Lunn wrote: > > > There is a very different approach, which might be simpler. > > > > > > We know polling will always work. And it should be possible to > > > transition between polling and interrupt at any point, so long as the > > > phylock is held. So if you get -EPROBE_DEFFER during probe, mark some > > > state in phydev that there should be an irq, but it is not around yet. > > > When the phy is started, and phylib starts polling, look for the state > > > and try getting the IRQ again. If successful, swap to interrupts, if > > > not, keep polling. Maybe after 60 seconds of polling and trying, give > > > up trying to find the irq and stick with polling. > > > > That doesn't sound like something that I'd backport to stable kernels. > > > What motivates me to make these changes in the first place is the idea > > that current kernels should work with updated device trees. > > By current, you mean old kernels, LTS etc. You want an LTS kernel to > work with a new DT blob? You want forward compatibility with a DT > blob. Do the stable rules say anything about that? > > Andrew Hmm, not sure about stable rules, but at least Marc Zyngier has suggested in the past that this is something which should work: https://lore.kernel.org/linux-arm-kernel/87czlzjxmz.wl-maz@xxxxxxxxxx/ To quote: | > 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.
