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

linux module kernel driver device
teerapap picture teerapap · Jan 5, 2009 · Viewed 15.5k times · Source

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 in my driver? I think they are both in the kernel so there might be a way that can use another driver directly.

Answer

Martin Carpenter picture Martin Carpenter · Jan 5, 2009

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

/* mod1.c */
#include <linux/module.h>
#include <linux/kernel.h>
#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 <linux/module.h>
#include <linux/kernel.h>
#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.

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