On Monday 17 February 2003 12:06, nils wrote:
> Hello,
>
> I have a little question concerning modules:
>
> In case I have the modules a and b.
>
> Is it right, that it isn't possible to have references from a to b and from
> b to a?
It is. This is a chicken-egg problem: who is first ? The insmod call
will always fail, as there are unresolved symbols.
>
> How can I achieve?
> I want to call procedures from a in b, and also some from b in a?
One solution would be, to estabish a 'client registering' functionality.
Say, a is the mother module, which is loaded first. For each reference to
b, it has some function pointer
static int (*b_func1)(int,...);
and some runtime wrapper
static int wrap_b_func1 (int, ...) {
if (!b_func1) return -ENODEV;
return b_func1(int,...);
}
Now, when b gets loaded, it calls a registering function in a, which
looks like
int b_registers_func1 ( int(*fun)(int,.) ) {
b_func1 = fun;
return 0;
}
>From now on, module a may call b using b_func1.
In the kernel sources, you will find a lot of algorithms similar to
- and better than - this. As an example, see the 'register_chrdev'
function.
>
> Do I have to write it as one module, or is there a better way?
For me, the answer is: if those two modules are that addicted
to functionalities of the other, they should be one.
Can one of them operate, without having its partner ?
>
> Thanks,
> Nils
HTH
Michael
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