Static function prototypes in kernel modules

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I'm reading LKM development manual and faced the following example when writing a device driver:

/*  
 *  Prototypes - this would normally go in a .h file
 */
int init_module(void);
void cleanup_module(void);
static int device_open(struct inode *, struct file *);
static int device_release(struct inode *, struct file *);
static ssize_t device_read(struct file *, char *, size_t, loff_t *);
static ssize_t device_write(struct file *, const char *, size_t, loff_t *);

The thing I was confused by was that it is proposed to put static non-inline declarations into a header file. What is the reason for that?

If we are not supposed to use these functions related to the driver anywhere except than in the 

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

static int init_module(void){
    int register_result = register_chrdev(&fops);
    //...
}

during module initialization then we can simply put their static definitions right here avoiding prototypes declaration. Otherwise they should (should?) be declared with external linkage.

kernel-module linux-kernel linux c
1 Answers

There is absolutely no needs to put static non-inline declarations into a separate header file.

In case of very complex driver definitions of device_* methods could be arranged into different source files (and definition of file_operations structure could be arranged into its own source file too), but in that case static specifier should be dropped.

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