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Old 08-22-2008, 02:04 AM   #1
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error: variable ‘fops’ has initializer but incomplete type

Dear All,
the source code and the error file attached here.
please remove the error.

Note: the important error is line no 69. as shown in the error file.
so how to solve that error.

Source code:

#define MODULE

#define SUCCESS 0
#define DEVICE_NAME "chardev" /* Dev name as it appears in /proc/devices */
#define BUF_LEN 80 /* Max length of the message from the device */

* Global variables are declared as static, so are global within the file.

static int Major; /* Major number assigned to our device driver */
static int Device_Open = 0; /* Is device open?
* Used to prevent multiple access to device */
static char msg[BUF_LEN]; /* The msg the device will give when asked */
static char *msg_Ptr;

struct file_operations fops = {
read: device_read,
write: device_write,
open: device_open,
release: device_release

* Called when a process tries to open the device file, like
* "cat /dev/mycharfile"
static int device_open(struct inode *inode, struct file *file)
/* static int counter = 0;

if (Device_Open)
return -EBUSY;

sprintf(msg, "I already told you %d times Hello world!\n", counter++);
msg_Ptr = msg;

return SUCCESS;*/
printk("In device open function \n");

* Called when a process closes the device file.
static int device_release(struct inode *inode, struct file *file)
// Device_Open--; /* We're now ready for our next caller */

* Decrement the usage count, or else once you opened the file, you'll
* never get get rid of the module.
// module_put(THIS_MODULE);

// return 0;

printk("IN device release function \n");

static struct file_operations fops = {
.open = device_open,
.release = device_release

int init_module(void)
Major = register_chrdev(0, DEVICE_NAME, &fops);

if (Major < 0) {
printk("Registering char device failed with %d\n", Major);
return Major;

printk("I was assigned major number %d. To talk to\n", Major);
return SUCCESS;

* This function is called when the module is unloaded
void cleanup_module(void)
int ret = unregister_chrdev(Major, DEVICE_NAME);
if (ret < 0)
printk("Error in unregister_chrdev: %d\n", ret);

The error file.

[root@localhost check]# gcc -c -O2 char.c
char.c:35: warning: ‘struct file’ declared inside parameter list
char.c:35: warning: its scope is only this definition or declaration, which is probably not what you want
char.c:35: warning: ‘struct inode’ declared inside parameter list
char.c:54: warning: ‘struct file’ declared inside parameter list
char.c:54: warning: ‘struct inode’ declared inside parameter list
char.c:69: error: variable ‘fops’ has initializer but incomplete type
char.c:70: error: unknown field ‘open’ specified in initializer
char.c:70: warning: excess elements in struct initializer
char.c:70: warning: (near initialization for ‘fops’)
char.c:71: error: unknown field ‘release’ specified in initializer
char.c:72: warning: excess elements in struct initializer
char.c:72: warning: (near initialization for ‘fops’)
[root@localhost check]#

please reply me how to solve the error.

Thank & Regards,
Rajkumar Halle
Old 08-24-2008, 08:57 AM   #2
Senior Member
Registered: Jun 2008
Distribution: debian, ubuntu, sidux
Posts: 1,125
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Rep: Reputation: 124Reputation: 124
I'd say your compiler doesn't like that initialization style, try this instead (don't forget to remove the /* */ you have surrounding it):

struct file_operations fops = {
  .read = device_read,
  .write = device_write,
  .open = device_open,
  .release = device_release


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