Messages in this thread | | | From | Michael Frank <> | Subject | Re: Golden rule: don't break userland (was Re: RFC: Starting a stable kernel series off the 2.6 kernel) | Date | Sun, 4 Dec 2005 16:37:39 +0100 |
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On Saturday 03 December 2005 19:43, Jeff Garzik wrote: > Adrian Bunk wrote: > > IOW, we should e.g. ensure that today's udev will still > > work flawlessly with kernel 2.6.30 (sic)? > > > > This could work, but it should be officially announced > > that e.g. a userspace running kernel 2.6.15 must work > > flawlessly with _any_ future 2.6 kernel. > > Fix the real problem: publicly shame kernel hackers that > change userland ABI/API without LOTS of notice, and > hopefully an old-userland compatibility solution > implemented. > > We change kernel APIs all the time. Having made that > policy decision, we have the freedom to rapidly improve > the kernel, and avoid being stuck with poor designs of > the past. > > Userland isn't the same. IMO sysfs hackers have > forgotten this. Anytime you change or remove sysfs > attributes these days, you have the potential to break > userland, which breaks one of the grand axioms of Linux. > Everybody knows "the rules" when it comes to removing > system calls, but forgets/ignores them when it comes to > ioctls, sysfs attributes, and the like.
WRT sysfs, sysfs is dynamic by design to accommodate individual HW configuration. Thus isn't this really a fault of user-space implementation?
> > Thus, I've often felt that heavy sysfs (and procfs) use > made it too easy to break userland. Maybe we should > change the sysfs API to include some sort of interface > versioning, or otherwise make it more obvious to the > programmer that they could be breaking userland compat.
You might need versions for every entry. I'd go for more documentation on proper use.
> > Offhand, once implemented and out in the field, I would > say a userland interface should live at least 1-2 years > after the "we are removing this interface" warning is > given. > > Yes, 1-2 years. Maybe even that is too small. We still > have old_mmap syscall around :) > > Jeff >
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