[Ipodlinux-devel] plugin-based programming in C

[Christopher F. <cf...@vi...>]

Hello all,

I've been using ipodlinux on my ipod for half a year or so, and i like
it a lot. Naturally, I thought I would take a peak at the source to see
if i could tweak things, maybe add a couple of features, etc.

The code was really nice to read. I'm pretty good in C myself, but I saw
a lot of things that I haven't really familiarized myself with 100% -
namely heavy use of function pointers and also a lot of type definitions
and functions being prefixed with an _ underscore.

I'm developing on an arm platform as well, [ arm9 - we have an mmu ] and
I'd like to put together a similar sort of extensible platform, so that
one can write modules for new applications. I'm hoping that this binds
all of the components closer together, so that I can start focusing on
architectural / model-driven design.

I'd like to pose a few questions if possible:

1) what are some of the best uses of function pointers? (i've already
experimented with them in typedef structs, but not really anywhere else)

2) when you prefix a typedef or function with an _ , it prevents that
symbol from being added into the object's symbol table, right? What is
the advantage of this exactly?

3) in podzilla2, the PZ_MOD_INIT() macro is used to ... oddly enough...
initialize a module. When someone is using this method for module
design, what are the minimally required functions that the module must
"export" this way? init(), run(), cleanup() ?

4) Does this plugin method require that the podzilla binary is
recompiled every time a new module is added? If not, what are the key
mechanisms that podzilla uses to browse the plugin directory and insert
'objects' at runtime?

5) Does each module recieve its own thread?

6) How is the global event system organized?



Many thanks,


~/Chris