main.c

linux设备驱动程序第三版及源代码

{
	struct scull_dev *dev = filp->private_data;
	struct scull_qset *dptr;
	int quantum = dev->quantum, qset = dev->qset;
	int itemsize = quantum * qset;
	int item, s_pos, q_pos, rest;
	ssize_t retval = -ENOMEM; /* value used in "goto out" statements */

	if (down_interruptible(&dev->sem))
		return -ERESTARTSYS;

	/* find listitem, qset index and offset in the quantum */
	item = (long)*f_pos / itemsize;
	rest = (long)*f_pos % itemsize;
	s_pos = rest / quantum; q_pos = rest % quantum;

	/* follow the list up to the right position */
	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;
	}
	/* write only up to the end of this quantum */
	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;

        /* update the size */
	if (dev->size < *f_pos)
		dev->size = *f_pos;

  out:
	up(&dev->sem);
	return retval;
}

/*
 * The ioctl() implementation
 */

int scull_ioctl(struct inode *inode, struct file *filp,
                 unsigned int cmd, unsigned long arg)
{

	int err = 0, tmp;
	int retval = 0;
    
	/*
	 * extract the type and number bitfields, and don't decode
	 * wrong cmds: return ENOTTY (inappropriate ioctl) before access_ok()
	 */
	if (_IOC_TYPE(cmd) != SCULL_IOC_MAGIC) return -ENOTTY;
	if (_IOC_NR(cmd) > SCULL_IOC_MAXNR) return -ENOTTY;

	/*
	 * the direction is a bitmask, and VERIFY_WRITE catches R/W
	 * transfers. `Type' is user-oriented, while
	 * access_ok is kernel-oriented, so the concept of "read" and
	 * "write" is reversed
	 */
	if (_IOC_DIR(cmd) & _IOC_READ)
		err = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));
	else if (_IOC_DIR(cmd) & _IOC_WRITE)
		err =  !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));
	if (err) return -EFAULT;

	switch(cmd) {

	  case SCULL_IOCRESET:
		scull_quantum = SCULL_QUANTUM;
		scull_qset = SCULL_QSET;
		break;
        
	  case SCULL_IOCSQUANTUM: /* Set: arg points to the value */
		if (! capable (CAP_SYS_ADMIN))
			return -EPERM;
		retval = __get_user(scull_quantum, (int __user *)arg);
		break;

	  case SCULL_IOCTQUANTUM: /* Tell: arg is the value */
		if (! capable (CAP_SYS_ADMIN))
			return -EPERM;
		scull_quantum = arg;
		break;

	  case SCULL_IOCGQUANTUM: /* Get: arg is pointer to result */
		retval = __put_user(scull_quantum, (int __user *)arg);
		break;

	  case SCULL_IOCQQUANTUM: /* Query: return it (it's positive) */
		return scull_quantum;

	  case SCULL_IOCXQUANTUM: /* eXchange: use arg as pointer */
		if (! capable (CAP_SYS_ADMIN))
			return -EPERM;
		tmp = scull_quantum;
		retval = __get_user(scull_quantum, (int __user *)arg);
		if (retval == 0)
			retval = __put_user(tmp, (int __user *)arg);
		break;

	  case SCULL_IOCHQUANTUM: /* sHift: like Tell + Query */
		if (! capable (CAP_SYS_ADMIN))
			return -EPERM;
		tmp = scull_quantum;
		scull_quantum = arg;
		return tmp;
        
	  case SCULL_IOCSQSET:
		if (! capable (CAP_SYS_ADMIN))
			return -EPERM;
		retval = __get_user(scull_qset, (int __user *)arg);
		break;

	  case SCULL_IOCTQSET:
		if (! capable (CAP_SYS_ADMIN))
			return -EPERM;
		scull_qset = arg;
		break;

	  case SCULL_IOCGQSET:
		retval = __put_user(scull_qset, (int __user *)arg);
		break;

	  case SCULL_IOCQQSET:
		return scull_qset;

	  case SCULL_IOCXQSET:
		if (! capable (CAP_SYS_ADMIN))
			return -EPERM;
		tmp = scull_qset;
		retval = __get_user(scull_qset, (int __user *)arg);
		if (retval == 0)
			retval = put_user(tmp, (int __user *)arg);
		break;

	  case SCULL_IOCHQSET:
		if (! capable (CAP_SYS_ADMIN))
			return -EPERM;
		tmp = scull_qset;
		scull_qset = arg;
		return tmp;

        /*
         * The following two change the buffer size for scullpipe.
         * The scullpipe device uses this same ioctl method, just to
         * write less code. Actually, it's the same driver, isn't it?
         */

	  case SCULL_P_IOCTSIZE:
		scull_p_buffer = arg;
		break;

	  case SCULL_P_IOCQSIZE:
		return scull_p_buffer;


	  default:  /* redundant, as cmd was checked against MAXNR */
		return -ENOTTY;
	}
	return retval;

}



/*
 * The "extended" operations -- only seek
 */

loff_t scull_llseek(struct file *filp, loff_t off, int whence)
{
	struct scull_dev *dev = filp->private_data;
	loff_t newpos;

	switch(whence) {
	  case 0: /* SEEK_SET */
		newpos = off;
		break;

	  case 1: /* SEEK_CUR */
		newpos = filp->f_pos + off;
		break;

	  case 2: /* SEEK_END */
		newpos = dev->size + off;
		break;

	  default: /* can't happen */
		return -EINVAL;
	}
	if (newpos < 0) return -EINVAL;
	filp->f_pos = newpos;
	return newpos;
}



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

/*
 * Finally, the module stuff
 */

/*
 * The cleanup function is used to handle initialization failures as well.
 * Thefore, it must be careful to work correctly even if some of the items
 * have not been initialized
 */
void scull_cleanup_module(void)
{
	int i;
	dev_t devno = MKDEV(scull_major, scull_minor);

	/* Get rid of our char dev entries */
	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);
	}

#ifdef SCULL_DEBUG /* use proc only if debugging */
	scull_remove_proc();
#endif

	/* cleanup_module is never called if registering failed */
	unregister_chrdev_region(devno, scull_nr_devs);

	/* and call the cleanup functions for friend devices */
	scull_p_cleanup();
	scull_access_cleanup();

}


/*
 * Set up the char_dev structure for this device.
 */
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;
	dev->cdev.ops = &scull_fops;
	err = cdev_add (&dev->cdev, devno, 1);
	/* Fail gracefully if need be */
	if (err)
		printk(KERN_NOTICE "Error %d adding scull%d", err, index);
}


int scull_init_module(void)
{
	int result, i;
	dev_t dev = 0;

/*
 * Get a range of minor numbers to work with, asking for a dynamic
 * major unless directed otherwise at load time.
 */
	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_minor, 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;
	}

        /* 
	 * allocate the devices -- we can't have them static, as the number
	 * can be specified at load time
	 */
	scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev), GFP_KERNEL);
	if (!scull_devices) {
		result = -ENOMEM;
		goto fail;  /* Make this more graceful */
	}
	memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev));

        /* Initialize each device. */
	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);
	}

        /* At this point call the init function for any friend device */
	dev = MKDEV(scull_major, scull_minor + scull_nr_devs);
	dev += scull_p_init(dev);
	dev += scull_access_init(dev);

#ifdef SCULL_DEBUG /* only when debugging */
	scull_create_proc();
#endif

	return 0; /* succeed */

  fail:
	scull_cleanup_module();
	return result;
}

module_init(scull_init_module);
module_exit(scull_cleanup_module);