* Linus Torvalds <[email protected]> wrote:
> On Wed, Aug 5, 2015 at 10:48 AM, Ingo Molnar <[email protected]> wrote:
> >>
> >> Some of these field names are visible to userspace and can't change.
> >
> > That's a misconception: bits in the uapi headers can be renamed just fine.
>
> I disagree. If it causes pain for user space, we just shouldn't do it.
Ok, agreed - I wanted to argue against the "can't change" statement and went
overboard with my own statement ...
Quite often headers can change and we've changed a number of fields in the past
-
but if they cause pain (as in this case) we don't do it.
So I'd say that based on past experience:
- changing small details in uapi headers is usually fine.
- changing small details in the ABI is usually not fine.
If anything breaks then the policy is the same, regardless of likelihood:
reverting the change.
> Some people copy the headers (preferred), others include the kernel header
> directory with a include path or a symlink, and it's damn painful if we start
> changing things that user space depends on.
>
> I'd say that it's like the ABI - if people don't really notice, you can do
> it,
> but if it breaks the build of a user app, we should be very very careful. The
> breakage is often hard to fix because of nasty versioning issues..
>
> Our goal in life really is "don't screw up user space".
Yeah, agreed 100%.
Thanks,
Ingo
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