Re: [RFCLUE3] flagging kernel interface changes

[William D Waddington <william.waddington@beezmo.com>]

Jesper Juhl wrote:
> On 15/11/06, William D Waddington <william.waddington@beezmo.com> wrote:
>
> > I tried submitting a patch a while back:
> > "[PATCH] IRQ: ease out-of-tree migration to new irq_handler prototype"
> > to add #define __PT_REGS to include/linux/interrupt.h to flag the change
> > to the new interrupt handler prototype.  It wasn't well received :(
> >
> > No big surprise.  The #define wasn't my idea and I hadn't submitted a
> > patch before.  I wanted to see how the patch procedure worked, and
> > hoped that the flag would be included so I could mod my drivers and
> > move on...
> >
> > What I'm curious about is why flagging kernel/driver interface changes
> > is considered a bad idea.  From my point of view as a low-life out-of-
> > tree driver maintainer,
> >
> > #ifdef NEW_INTERFACE
> > #define <my new internals>
> > #endif
> >
> > (w/maybe an #else...)
> >
> > is cleaner and safer than trying to track specific kernel versions in
> > a multi-kernel-version driver.  It seems that in some cases, the new
> > interface has been, like HAVE_COMPAT_IOCTL for instance.
> >
> > I don't want to start an argument about "stable_api_nonsense" or the
> > wisdom of out-of-tree drivers.  Just curious about the - why - and
> > whether it is indifference or antagonism toward drivers outside the
> > fold. Or ???
>
> I would say that one reason is that cluttering up the kernel with
> #ifdef's is ugly and annoying to maintain long-term. Especially when
> it's expected that anyone who changes in-kernel interfaces also fix up
> any user(s) of those interfaces, so the #ifdef's are pointless
> (ignoring out-of-tree code that is).

Ah, but out-of-tree code is what I'm stuck w/maintaining.  I wouldn't
want to infest in-tree drivers w/#ifdef's either, but they are a fact
of life in my world.  And, lately, _really_ ugly version tests.

If I had _my_ way, there would be a kernel_interface_change.h file that
had an #define'd entry for _every_ kernel interface change within a
major release series:

/*
 * include/linux/interrupt.h interface change x.y.z
 * interrupt handler now takes 2 args
 */
#define INTERRUPT_H_CHANGE_X.Y.Z "interrupt handler now takes 2 args"

or something.

I understand that many (most?) kernel maintainers would prefer that
all drivers be brought in-tree, and aren't particularly concerned
when interface changes affect out-of-tree drivers.

Respectfully, I suggest that world domination isn't quite the same
thing as world dictatorship, and maybe the road to the former would
be helped by a little less of the latter :)

Rat-bastard out-of-tree maintainer takes refuge under desk....

Thanks,
Bill
--
--------------------------------------------
William D Waddington
Bainbridge Island, WA, USA
william.waddington@beezmo.com
--------------------------------------------
"Even bugs...are unexpected signposts on
the long road of creativity..." - Ken Burtch
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