Global variables in multi-file device driver

[agaurav]

Hi,

I am writing a Linux Device driver for 2.6 kernel (for the first time). There is plenty of code so I decided to split it into 2 files. I have 2 global variables that I want both files to use. I could use function parameters but that would be way too cumbersome unfortunately. I can't get this to work though.
----------

first.c
#include <linux/module.h>
....
....
char *mem_ptr;

static int __init my_init()  {
....
}

----------

second.c
#include <linux/module.h>
....
....
extern char *mem_ptr;

function compute()  {
   mem_ptr = NULL;
....
}

I get a build (link) time warning as follows:

  Building modules, stage 2.
  MODPOST
*** Warning: "mem_ptr" [/home/guraaf/first.ko] undefined!

Any ideas why doesn't the extern pick up the global variable from the other file? Do I have my makefile incorrectly defined. It is:

obj-m   := first.o 
first-objs := first.o second.o

module:
        $(MAKE) -C $(KERNELDIR) ARCH=ppc M=$(PWD) modules

[rakeshkumar]

in second.c file

char variable;
EXPORT_SYMBOL(variable);

and use it in first.c file..the above will export the variable to global symbol table so that u can use it anywhere in any module.. remove the extern and try once..

[agaurav]

Hi,
Thanks for replying. The problem was that the .tmp_versions got into a bad state. As soon as I deleted that direcory everything started working.