An example of cdev driver

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Link :http://blog.csdn.net/nhczp/article/details/4643845

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#include

/* Per-device (per-bank) structure */

struct cmos_dev {
  unsigned short current_pointer; /* Current pointer within the bank */
  unsigned int size; /* Size of the bank */
  int bank_number; /* CMOS bank number */
  struct cdev cdev; /* The cdev structure */
  char name[10]; /* Name of I/O region */
  /* ... */ /* Mutexes, spinlocks, wait queues, .. */
} *cmos_devp;



/* File operations structure. Defined in linux/fs.h */
static struct file_operations cmos_fops = {
  .owner = THIS_MODULE, /* Owner */
  .open = cmos_open, /* Open method */
  .release = cmos_release, /* Release method */
  .read = cmos_read, /* Read method */
  .write = cmos_write, /* Write method */
  .llseek = cmos_llseek, /* Seek method */
  .ioctl = cmos_ioctl, /* Ioctl method */
};



static dev_t cmos_dev_number; /* Allotted device number */
struct class *cmos_class; /* Tie with the device model */


#define NUM_CMOS_BANKS 2
#define CMOS_BANK_SIZE (0xFF*8)
#define DEVICE_NAME "cmos"
#define CMOS_BANK0_INDEX_PORT 0x70
#define CMOS_BANK0_DATA_PORT 0x71
#define CMOS_BANK1_INDEX_PORT 0x72
#define CMOS_BANK1_DATA_PORT 0x73


unsigned char addrports[NUM_CMOS_BANKS] = {CMOS_BANK0_INDEX_PORT,
  CMOS_BANK1_INDEX_PORT,};

unsigned char dataports[NUM_CMOS_BANKS] = {CMOS_BANK0_DATA_PORT,
CMOS_BANK1_DATA_PORT,};

/*
* Driver Initialization
*/

int __init
cmos_init(void)
{
int i;

/* Request dynamic allocation of a device major number */
if (alloc_chrdev_region(&cmos_dev_number, 0,
NUM_CMOS_BANKS, DEVICE_NAME) < 0) {
printk(KERN_DEBUG "Can't register device/n"); return -1;
}

/* Populate sysfs entries */
cmos_class = class_create(THIS_MODULE, DEVICE_NAME);

for (i=0; i/* Allocate memory for the per-device structure */
cmos_devp = kmalloc(sizeof(struct cmos_dev), GFP_KERNEL);
if (!cmos_devp) {
printk("Bad Kmalloc/n"); return 1;
}


  /* Request I/O region */
sprintf(cmos_devp->name, "cmos%d", i);
if (!(request_region(addrports[i], 2, cmos_devp->name)) {
printk("cmos: I/O port 0x%x is not free./n", addrports[i]);
return –EIO;}

/* Fill in the bank number to correlate this device
with the corresponding CMOS bank */
cmos_devp->bank_number = i;

/* Connect the file operations with the cdev */
cdev_init(&cmos_devp->cdev, &cmos_fops);
cmos_devp->cdev.owner = THIS_MODULE;


/* Connect the major/minor number to the cdev */
if (cdev_add(&cmos_devp->cdev, (dev_number + i), 1)) {
printk("Bad cdev/n");
return 1;
}


/* Send uevents to udev, so it'll create /dev nodes */
class_device_create(cmos_class, NULL, (dev_number + i),
NULL, "cmos%d", i);
}

printk("CMOS Driver Initialized./n");
return 0;
}




/* Driver Exit */

void __exit
cmos_cleanup(void)
{

int i;
/* Remove the cdev */
cdev_del(&cmos_devp->cdev);

/* Release the major number */
unregister_chrdev_region(MAJOR(dev_number), NUM_CMOS_BANKS);
/* Release I/O region */
for (i=0; iclass_device_destroy(cmos_class, MKDEV(MAJOR(dev_number), i));
release_region(addrports[i], 2);

}
/* Destroy cmos_class */
class_destroy(cmos_class);
return();
}


module_init(cmos_init);
module_exit(cmos_cleanup);