Linux Device Drivers, Second Edition

Quick Reference

This chapter introduced the following symbols and header files. The list of the fields in struct file_operations and struct file is not repeated here.

#include <linux/fs.h>

The “file system” header is the header required for writing device drivers. All the important functions are declared in here.

int register_chrdev(unsigned int major, const char *name, struct file_operations *fops);

Registers a character device driver. If the major number is not 0, it is used unchanged; if the number is 0, then a dynamic number is assigned for this device.

int unregister_chrdev(unsigned int major, const char *name);

Unregisters the driver at unload time. Both major and the name string must contain the same values that were used to register the driver.

kdev_t inode->i_rdev;

The device “number” for the current device is accessible from the inode structure.

int MAJOR(kdev_t dev); , int MINOR(kdev_t dev);

These macros extract the major and minor numbers from a device item.

kdev_t MKDEV(int major, int minor);

This macro builds a kdev_t data item from the major and minor numbers.

SET_MODULE_OWNER(struct file_operations *fops)

This macro sets the owner field in the given file_operations structure.

#include <asm/semaphore.h>

Defines functions and types for the use of semaphores.

void sema_init (struct semaphore *sem, int val);

Initializes a semaphore to a known value. Mutual exclusion semaphores are usually initialized to a value of 1.

int down_interruptible ...