Nested class devices and the future of the device model [LWN.net]

Nested class devices and the future of the device model

Posted Oct 20, 2005 18:57 UTC (Thu) by iabervon (subscriber, #722)
In reply to: Nested class devices and the future of the device model by kleptog
Parent article: Nested class devices and the future of the device model

If there were an unstable branch, it would presumably break compatibility with 2.6, and it would be intended to become the future arrangement. And you would therefore definitely be wasting effort moving to 2.6, because the stuff you'd use wouldn't even be intended to work long-term. Having stable and unstable branches doesn't in any way resolve compatibility issues; it's just an excuse for breaking things.

I'd even venture to say that the fact that you're still using 2.4 and not 2.6 is that there's a lot of incompatibility due to the 2.5 series in between. Going from 2.6.0 to 2.6.13 breaks compatibility less than 2.4.27 to 2.6.0, even though there is more total change, because there isn't the expectation that there will be a major transition that changes everything.

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Nested class devices and the future of the device model

Posted Oct 20, 2005 20:08 UTC (Thu) by kleptog (subscriber, #1183) [Link]

Maybe, maybe not. Near as I can tell you need different versions of udev and hotplug depending on whether you're running 2.6.8, 2.6.13 or (soon) 2.6.16. No matter which way you turn it they're changing user-visible interfaces every other release in a backward incompatable way.

It's a change though. During the 2.4 series I would regularly upgrade my kernel, fairly secure in the knowledge that after the reboot everything would just work. With 2.6 you upgrade and find that your module loading just broke, again. I'm glad there's a lot of guinea pigs out there willing to test the stuff, because I have a day job and work to do. Call me back we 2.8 releases and 2.6 stablises.

Nested class devices and the future of the device model

Posted Oct 20, 2005 21:22 UTC (Thu) by iabervon (subscriber, #722) [Link]

Switch to 2.6.13.x, and apply backported security patches. The new scheme essentially pushes the "everything stays the same" level down a digit, so 2.6.13 to 2.6.14 is essentially like 2.2 to 2.4, except that it won't break nearly as much. The main caveat is that I think it's worth waiting either for 2.6.x.1 or for 2.6.x to turn out stable, because the quality control on 2.6.x as first released isn't that good; 2.6.x is the point at which the version is turned over to the "stable" maintainers, not their first release.

I also haven't heard anything about module loading breaking, except for between 2.4 to 2.6. There has been code that's had bugs, and if it's built as a module, it causes problems when you load it, but that's hardly the same thing, and it isn't unlike problems that crop up on occasion in 2.4.