【Linux设备驱动程序（第三版）】----Scull

 【Linux设备驱动程序（第三版）】----Scull

Scull.c

#include 
#include 
#include 
#include //file_operations, file
#include //cdev
#include //copy_to_user & copy_from_user

MODULE_LICENSE("Dual BSD/GPL");

int scull_major = 250;
int scull_minor = 0;
int scull_nr_devs = 4;
int scull_quantum = 4000;
int scull_qset = 1000;

module_param(scull_major, int, S_IRUGO);
module_param(scull_minor, int, S_IRUGO);
module_param(scull_nr_devs, int, S_IRUGO);
module_param(scull_quantum, int, S_IRUGO);
module_param(scull_qset, int, S_IRUGO);

struct scull_qset {
	void **data;
	struct scull_qset *next;
};

struct scull_dev{
	struct scull_qset *data;
	int quantum;
	int qset;
	unsigned long size;
	unsigned int access_key;
	struct semaphore sem;
	struct cdev cdev;
};

struct scull_dev *scull_devices;

int scull_trim(struct scull_dev *dev)
{
	struct scull_qset *next, *dptr;
	int qset = dev->qset;
	int i;

	for(dptr = dev->data; dptr; dptr = next){
		if(dptr->data){
			for(i = 0; i < qset; i++)
				kfree(dptr->data[i]);
			kfree(dptr->data);
			dptr->data = NULL;
		}
		next = dptr->next;
		kfree(dptr);
	}

	dev->size = 0;
	dev->quantum = scull_quantum;
	dev->qset = scull_qset;
	dev->data = NULL;
	return 0;
}

int scull_open(struct inode *inode, struct file *filp)
{
	struct scull_dev *dev;
	
	dev = container_of(inode->i_cdev, struct scull_dev, cdev);
	filp->private_data = dev;

	if(filp->f_flags & O_ACCMODE == O_WRONLY){
		scull_trim(dev);
	}
	return 0;
}

int scull_release(struct inode *inode, struct file *filp)
{
	return 0;
}

struct scull_qset *scull_follow(struct scull_dev *dev, int n)
{
	struct scull_qset *qs = dev->data;

	if(!qs){
		qs = dev->data = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
		if(qs == NULL)
			return NULL;
		memset(qs, 0, sizeof(struct scull_qset));
	}

	while(n--){
		if(!qs->next){
			qs->next = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
			if(qs->next == NULL)
				return NULL;
			memset(qs->next, 0, sizeof(struct scull_qset));
		}
		qs = qs->next;
		continue;		
	}
	return qs;
}

ssize_t scull_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
	printk(KERN_NOTICE "Enter scull_read\n");
	struct scull_dev *dev = filp->private_data;
	struct scull_qset *dptr;
	int quantum = dev->quantum;
	int qset = dev->qset;
	int itemsize = quantum * qset;
	int item, s_pos, q_pos, rest;
	ssize_t retval = 0;

	if(down_interruptible(&dev->sem))
		return -ERESTARTSYS;
	
	if(*f_pos >= dev->size)
		goto out;

	if(*f_pos + count > dev->size)
		count = dev->size - *f_pos;

	item = (long)*f_pos / itemsize;
	rest = (long)*f_pos % itemsize;

	s_pos = rest / quantum;
	q_pos = rest % quantum;

	dptr = scull_follow(dev, item);
	
	if(dptr == NULL || !dptr->data || !dptr->data[s_pos])
		goto out;

	if(count > quantum - q_pos)
		count = quantum - q_pos;

	if(copy_to_user(buf, dptr->data[s_pos] + q_pos, count)){
		retval = -EFAULT;
		goto out;
	}
	
	*f_pos += count;
	retval = count;
	out:	
		up(&dev->sem);
		return retval;
}

ssize_t scull_write(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
	printk(KERN_NOTICE "Enter scull_write\n");
	struct scull_dev *dev = filp->private_data;
	struct scull_qset *dptr;
	int quantum = dev->quantum;
	int qset = dev->qset;
	int itemsize = quantum * qset;
	int item, s_pos, q_pos, rest;
	ssize_t retval = -ENOMEM;

	if(down_interruptible(&dev->sem))
		return -ERESTARTSYS;
	
	item = (long)*f_pos / itemsize;
	rest = (long)*f_pos % itemsize;

	s_pos = rest / quantum;
	q_pos = rest % quantum;

	dptr = scull_follow(dev, item);
	if(dptr == NULL)
		goto out;

	if(!dptr->data){
		dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL);
		if(!dptr->data)
			goto out;
		memset(dptr->data, 0, qset * sizeof(char *));
	}	
	if(!dptr->data[s_pos]){
		dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL);
		if(!dptr->data[s_pos])
			goto out;
	}

	if(count > quantum - q_pos)
		count = quantum - q_pos;

	if(copy_from_user(dptr->data[s_pos] + q_pos, buf,  count)){
		retval = -EFAULT;
		goto out;
	}
	
	*f_pos += count;
	retval = count;

	if(dev->size < *f_pos)
		dev->size = *f_pos;
	out:	
		up(&dev->sem);
		return retval;
}

struct file_operations scull_fops = {
	.owner = THIS_MODULE,
	.open = scull_open,
	.release = scull_release,
	.read = scull_read,
	.write = scull_write,
	
};

static void scull_setup_cdev(struct scull_dev *dev, int index)
{
	int err, devno = MKDEV(scull_major, scull_minor + index);

	cdev_init(&dev->cdev, &scull_fops);
	dev->cdev.owner = THIS_MODULE;
	err = cdev_add(&dev->cdev, devno, 1);
	if(err)
		printk(KERN_NOTICE "Error %d adding scull%d", err, index);
}


static void scull_cleanup_module(void)
{
	printk(KERN_ALERT "Goodbye,world!\n");
	int i;
	dev_t devno = MKDEV(scull_major, scull_minor);

	if(scull_devices){
		for(i = 0; i < scull_nr_devs; i++){
			scull_trim(scull_devices + i);
			cdev_del(&scull_devices[i].cdev);
		}
		kfree(scull_devices);
	}

	unregister_chrdev_region(devno, scull_nr_devs);
}

static int __init scull_init_module(void)
{
	printk(KERN_ALERT "Hello, World!\n");
	int result, i;
	dev_t dev = 0;

	if(scull_major){
		dev = MKDEV(scull_major, scull_minor);
		result = register_chrdev_region(dev, scull_nr_devs, "scull");
	}else{
		result = alloc_chrdev_region(&dev, scull_major, scull_nr_devs, "scull");
		scull_major = MAJOR(dev);
	}

	if(result < 0){
		printk(KERN_WARNING "scull:can't get major %d\n", scull_major);
		return result;
	}

	scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev), GFP_KERNEL);	
	if(!scull_devices){
		result = -ENOMEM;
		goto fail;
	}	
	memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev));

	for(i = 0; i < scull_nr_devs; i++){
		scull_devices[i].quantum = scull_quantum;
		scull_devices[i].qset = scull_qset;
		init_MUTEX(&scull_devices[i].sem);
		scull_setup_cdev(&scull_devices[i], i);
	}
	

	return 0;

fail:
		scull_cleanup_module();
		return result;
}


module_init(scull_init_module);
module_exit(scull_cleanup_module);

Makefile

 

obj-m:= Scull.o
modules-objs:= Scull.o

KDIR:= /usr/src/linux-headers-2.6.31-14-generic/
PWD:= $(shell pwd)

default:
	make -C $(KDIR) M=$(PWD) modules
clean:
	rm -rf *.ko *.mod.c *.mod.o *.o *.markers *.symvers *.order

 

创建设备节点

mknod /dev/scull0 c 250 0
mknod /dev/scull1 c 250 1
mknod /dev/scull2 c 250 2
mknod /dev/scull3 c 250 3

测试

echo "Test" > /dev/scull0 
cat /dev/scull0 
Test