Date: Thu, 3 Jan 2008 18:19:05 -0800 From: Alfred Perlstein <alfred@freebsd.org> To: Julian Elischer <julian@elischer.org> Cc: arch@freebsd.org Subject: Re: RFC: sysctl additional functions/macros Message-ID: <20080104021905.GE76698@elvis.mu.org> In-Reply-To: <477D931D.4000303@elischer.org> References: <477D931D.4000303@elischer.org>
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Yes, but EINVAL please.
Another idea would be a simplified SYSCTL_INT_PROC
that allowed one to define a function like so:
int
sysctl_handle_int_proc(void *handle, int *newval, int *max, int *min)
{
}
If this function returned '0' then 'newval' would be accepted.
Otherwise the function should return an error, most likely EINVAL.
The point being that a lot of these maximums may take a calculation
and we should make it as easy as possible to do this calculation
and provide the function for doing so.
One would also set the min/max values so that one could query
the acceptable bounds of a tunable, or even the bounds of of
the tuneable.
(Note: if *newval == NULL, we're just querying max/min, not
doing a set operation.)
(Note 2: "handle" is so you can have a common handler and
possibly switch() off of handle for multiple sysctl ints to
reduce the number of functions required.)
-Alfred
* Julian Elischer <julian@elischer.org> [080103 17:57] wrote:
> I would like to extend the current SYSCTL_INT() with
> SYSCTL_INT_CLAMPED() or similar, where you also supply a
> maximum acceptable value. (and maybe a clue as to what to say if it is
> a bad value).
>
> so many users of SYSCTL_INT don't check for bad values because it's so
> much harder (you need to supply your own handler), and so many
> simple handlers exist fo rthe people that DO check that it seems to
> me that we should provide a pre-canned way to do this....
>
> we are limited to using the existing structure,
> but as we have no existing callers we can redefine
> one element....
>
> I would suggest:
>
> I'd like to test for a minimum too but I think I can only squeeze one
> field out of the existing struct sysctl_oid.
>
> SYSCTL_INT_CLAMPED(parent, nbr, name, access, ptr, max, descr)
> ^^^^
>
> anyone think it's a bad idea?
> After all the macros are evaluated, (etc.) it would call:
> ( off the top of my head )
>
> int
> sysctl_handle_int_max(SYSCTL_HANDLER_ARGS)
> {
> int error = 0;
>
> error = SYSCTL_OUT(req, arg1, sizeof(int));
>
> if (error || !req->newptr)
> return (error);
>
> if (*(int *)arg1 > (int)arg2)
> error = EDOOFUS;
> else
> error = SYSCTL_IN(req, arg1, sizeof(int));
> return (error);
> }
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--
- Alfred Perlstein
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