drv.c

这是ARM9 linux 2.4.X 字符驱动开发例子

/*  leddrv.c - Create an input/output character device
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h> 	/* for -EBUSY */
#include <linux/ioport.h>	/* for verify_area */
#include <linux/init.h>		/* for module_init */
#include <asm/uaccess.h>  	/* for get_user and put_user */
#include <asm-arm/arch-s3c2410/S3C2410.h>

#include "drv.h"

#define 	BUF_LEN 		4
#define 	DEVICE_NAME 	"char_dev"

static int 	Device_Open = 0;
static char Message[BUF_LEN];
static char *Message_Ptr;

int 	device_ioctl(struct inode *,struct file *,unsigned int ,unsigned long ); 	

/* This function is called whenever a process attempts 
 * to open the device file */
static int device_open(struct inode *inode, struct file *file)
{
  printk("Device Open\n");

  /* We don't want to talk to two processes at the 
   * same time */
  if (Device_Open) return -EBUSY;

  Device_Open++;
  
  MOD_INC_USE_COUNT;

  /* Initialize the message */
  Message_Ptr = Message;

  return 0;
}

/* This function is called when a process closes the 
 * device file. It doesn't have a return value because 
 * it cannot fail. Regardless of what else happens, you 
 * should always be able to close a device (in 2.0, a 2.2
 * device file could be impossible to close).
 */
static int device_release(struct inode *inode, struct file *file)
{
  printk(("device_release\n"));

  /* We're now ready for our next caller */
  Device_Open --;

  MOD_DEC_USE_COUNT;

  return 0;
}

static int flags = 0xff;
/* This function is called whenever a process which 
 * has already opened the device file attempts to 
 * read from it. */
static ssize_t device_read(
    struct file *file,
    char *buffer, 		/* The buffer to fill with the data */   
    size_t length,     	/* The length of the buffer */
    loff_t *offset) 	/* offset to the file */
{
  /* Number of bytes actually written to the buffer */
  int 	bytes_read = 4;
  int * data=(int *)buffer;
  char  str[256];

  sprintf(str, "device_read %d\n", flags);
  printk((str));

  put_user(flags, data);  
   /* Read functions are supposed to return the number 
    * of bytes actually inserted into the buffer */
  return bytes_read;
}


/* This function is called when somebody tries to 
 * write into our device file. */ 
static ssize_t device_write(struct file *file, const char *buffer, size_t length, loff_t *offset)
{
  int 	value;
  int 	bytes_writes = 4;
  int* 	data = (int*)buffer;
  char  str[256];

  get_user(value, data);
  flags = value;
  sprintf(str, "device_write %d\n", flags);
  printk((str));
  
  /* Again, return the number of input characters used */
  return bytes_writes;
};

/* This function is called whenever a process tries to 
 * do an ioctl on our device file. We get two extra 
 * parameters (additional to the inode and file 
 * structures, which all device functions get): the number
 * of the ioctl called and the parameter given to the 
 * ioctl function.
 *
 * If the ioctl is write or read/write (meaning output 
 * is returned to the calling process), the ioctl call 
 * returns the output of this function.
 */
int device_ioctl(
    struct inode *inode,
    struct file *file,
    unsigned int ioctl_num,/* The number of the ioctl */
    unsigned long ioctl_param) /* The parameter to it */
{
  int	temp;
  int* 	data;
  int   ioctl;
  char  str[256];

  printk(("Device_ioctl\n"));
  
  /* Switch according to the ioctl called */
  switch (ioctl_num) 
  {
    case IOCTL_SET_MSG:
      /* Receive a pointer to a message (in user space) 
       * and set that to be the device's message. */ 

      /* Get the parameter given to ioctl by the process */
      data = (int*) ioctl_param;
      
      get_user(temp, data);
      sprintf(str, "Device_ioctl SET_MSG %d\n", temp);
      printk((str));
      
      break;

    case IOCTL_GET_MSG:
    
      printk(("Device_ioctl PUT_MSG\n"));

      break;
  }

  return 0;
};

/* Module Declarations *************************** */
/* This structure will hold the functions to be called 
 * when a process does something to the device we 
 * created. Since a pointer to this structure is kept in 
 * the devices table, it can't be local to
 * init_module. NULL is for unimplemented functions. */
struct file_operations Fops = {
	.read 		= device_read, 
	.write 		= device_write,
	.open 		= device_open,
	.release 	= device_release,
	.ioctl		= device_ioctl
	};

/* Initialize the module - Register the character device */
static int __init led_module_init( void )
{
    	int ret_val;
  
  /* Register the character device (atleast try) */
  ret_val = register_chrdev(MAJOR_NUM, DEVICE_NAME, &Fops);

  /* Negative values signify an error */
  if (ret_val < 0) {
    printk ("%s failed with %d\n",
            "Sorry, registering the character device ",
            ret_val);
    return ret_val;
  }
  
  printk ("%s The major device number is %d.\n",
          "Registeration is a success", 
          MAJOR_NUM);
          
  printk ("If you want to talk to the device driver,\n");
  printk ("you'll have to create a device file. \n");
  printk ("We suggest you use:\n");
  printk ("mknod %s c %d 0\n", DEVICE_FILE_NAME,MAJOR_NUM);
  printk ("The device file name is important, because\n");
  printk ("the ioctl program assumes that's the\n");
  printk ("file you'll use.\n");

  return 0;
};

/* Cleanup - unregister the appropriate file from /proc */
static void __exit led_module_cleanup(void)
{
  int ret;
  
//  release_region(LED_BASE, 12);

  /* Unregister the device */
  ret = unregister_chrdev(MAJOR_NUM, DEVICE_NAME);
 
  /* If there's an error, report it */ 
  if (ret < 0)
    printk("Error in module_unregister_chrdev: %d\n", ret);
};

module_init(led_module_init);
module_exit(led_module_cleanup);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Cvtech Co., Ltd <http://www.cvtech.com.cn>");
MODULE_DESCRIPTION("LED char driver");