Device Driver Functions Reference

 

#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);

 Register 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 struct.

 

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_MUDULE_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 ues 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(struct semaphore *sem);

void up(struct semaphore *sem);

 Obtains a semaphore (sleeping,if necessary) and releases it, respectively.

 

#include<asm/segment.h>

#include<asm/uaccess.h>

 segment.h defines functions related to cross-space copying in all kernels up to and including 2.0.The name was changed to uaccess.h in the 2.1 development series.

 

unsigned long _ _copy_from_user (void *to,const void *from, unsigned long count);

unsigned long _ _copy_to_user(void *to,const void *from,unsigned long count);

 Copy data between user space and kernel space.

 

void memcpy_fromfs(void *to,const void *from,unsigned long count);

void memcpy_tofs(void *to,const void *from,unsigned long count);

 These functions were used to copy an array of bytes from user space to kernel space and vice versa in version 2.0 of the kernel.

 

#include<linux/devfs_fs_kernel.h>

devfs_handle_t devfs_mk_dir(devfs_handle_t dir, const char *name,void *info);

devfs_handle_t devfs_register(devfs_handle_t dir, const char *name,unsigned int flags, unsigned int major, unsigned int minor, umode_t mode, void *ops, void *info);

void devfs_unregister(devfs_handle_t de);

 These are the basic functions for registering devices with the device filesystem(devfs);