Basic Of Char Driver

The list of the fields in struct file_operations and struct file is not repeated here.
#include <linux/types.h>
dev_t
dev_t is the type used to represent device numbers within the kernel.
int MAJOR(dev_t dev);
int MINOR(dev_t dev);
Macros that extract the major and minor numbers from a device number.
dev_t MKDEV(unsigned int major, unsigned int minor);
Macro that builds a dev_t data item from the major and minor numbers.
#include <linux/fs.h>
The “filesystem” header is the header required for writing device drivers. Many
important functions and data structures are declared in here.
int register_chrdev_region(dev_t first, unsigned int count, char *name)
int alloc_chrdev_region(dev_t *dev, unsigned int firstminor, unsigned int
count, char *name)
void unregister_chrdev_region(dev_t first, unsigned int count);
Functions that allow a driver to allocate and free ranges of device numbers.
register_chrdev_region should be used when the desired major number is known
in advance; for dynamic allocation, use alloc_chrdev_region instead.
int register_chrdev(unsigned int major, const char *name, struct file_operations
*fops);
The old (pre-2.6) char device registration routine. It is emulated in the 2.6 kernel
but should not be used for new code. If the major number is not 0, it is used
unchanged; otherwise a dynamic number is assigned for this device.
int unregister_chrdev(unsigned int major, const char *name);
Function that undoes a registration made with register_chrdev. Both major and
the name string must contain the same values that were used to register the
driver.
struct file_operations;
struct file;
struct inode;
Three important data structures used by most device drivers. The file_operations
structure holds a char driver’s methods; struct file represents an open file, and
struct inode represents a file on disk.
#include <linux/cdev.h>
struct cdev *cdev_alloc(void);
void cdev_init(struct cdev *dev, struct file_operations *fops);
int cdev_add(struct cdev *dev, dev_t num, unsigned int count);
void cdev_del(struct cdev *dev);
Functions for the management of cdev structures, which represent char devices
within the kernel.
#include <linux/kernel.h>
container_of(pointer, type, field);
A convenience macro that may be used to obtain a pointer to a structure from a
pointer to some other structure contained within it.
#include <asm/uaccess.h>
This include file declares functions used by kernel code to move data to and
from user space.
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.