On pointer type and the return type of ioremap

[Grissiom]

Hi all,

I'm writing my little module now a days and want to ioremap some space. I
learnt from LDD3 that "Therefore, generic memory addresses in the kernel
are usually unsigned long"(ch11). So I declared a pointer like "usigned
long p2dev;" But when I feed it with ioremap, it yields a warning:

warning: assignment makes integer from pointer without a cast [enabled by
default]

Do I really have to add a cast? What is the reason that while "generic
pointers are unsigned long" but the return type of ioremap is void *?

Thanks in advance.

-- 
Cheers,
Grissiom
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