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SubjectRe: [PATCH] CONFIG_KMOD needs to be default y
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On Tue, 2008-07-08 at 23:03 +1000, Rusty Russell wrote:

> > What about just killing the config option entirely? It' basically
> > guarding a ~50 lines function + a sysctl variable. I think having
> > modules but not CONFIG_KMOD is entirely unreasonable.
>
> I agree with Christoph here.

Yeah, like I said, I wasn't sure why it's there anyway.

> But as a patch series please: it's spread pretty wide. eg. first make it a
> non-prompting CONFIG option, then remove the users, then finally kill it.

Sure.

> Some existing request_module users might be able to use
> try_then_request_module, too...

try_then_request_module seems buggy though. Or at least, doing something
unexpected. Here's the macro, for reference:

#define try_then_request_module(x, mod...) ((x) ?: (request_module(mod), (x)))

I think it should be
#define try_then_request_module(x, mod...) \
((x) ?: ({request_module(mod); (x)}))

the difference being that it returns the result of the second "x" when
the first "x" fails. A potential user would be
net/bridge/netfilter/ebtables.c:

ret = find_inlist_lock_noload(head, name, error, mutex);
if (!ret) {
request_module("%s%s", prefix, name);
ret = find_inlist_lock_noload(head, name, error, mutex);
}

which could then be written as

ret = try_then_request_module(
find_inlist_lock_noload(head, name, error, mutex),
"%s%s", prefix, name);

Also, in the case of MODULES=n, I think it should just be

static inline void printf_check(char *name, ...) __attribute__((format(printf, 1, 2))) {};
#define try_then_request_module(x, mod...) \
({ printf_check(mod); (x) })

so (x) is only evaluated once.

A different variation you could make a case for is to not re-evaluate x
if request_module fails, which would then automatically collapse the
MODULES=n case:

#define try_then_request_module(x, mod...) \
({ typeof(x) __ret = (x); __ret ?: \
(request_module(mod) ? __r : (x)); })

johannes
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