sharing persisten cache between modules

[Bart Ogryczak]

Hi,
I´ve got a problem creating persistent cache, that would be shared
between modules. There a supermodule, which calls submodules. I´d like
submodules to use cache created in the supermodule. The only way I see
right now, is to pass it as function argument, but that would require a
change in API, which I´d prefer to avoid. Is this the only way?