How to write Linux driver module call/use another driver module?

Question

I\'m developing a Linux driver loadable module and I have to use another device in my driver.(kind of driver stacked on another driver)

How do I call/use another driver

Answer 1

You will need the EXPORT_SYMBOL (or EXPORT_SYMBOL_GPL) macro. For example:

/* mod1.c */
#include 
#include 
#include "mod1.h"
....
void mod1_foo(void)
{
    printk(KERN_ALERT "mod1_foo\n");
}
EXPORT_SYMBOL(mod1_foo);

/* mod2.h */
....
extern void mod1_foo(void);
....

/* mod2.c */
#include 
#include 
#include "mod1.h"
#include "mod2.h"
int init_module(void)
{
    mod1_foo();
    ...

This should be plain sailing, but you must of course be careful with the namespace - stomping on somebody else's kernel module symbols would be unfortunate.