staging: comedi: refactor sysfs files in comedi_fops.c

Refactor the sysfs attributes and functions to remove
the need for the forward declarations and use the
DEVICE_ATTR macro to define them.

Instead of individually creating sysfs device attribute
files, wrap them in an attribute_group and use the
sysfs_create_group function to create them.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Mori Hess <fmhess@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_fops.c

@@ -129,15 +129,295 @@ static int do_cancel(struct comedi_device *dev, struct comedi_subdevice *s);
 static int comedi_fasync(int fd, struct file *file, int on);
 
 static int is_device_busy(struct comedi_device *dev);
+
 static int resize_async_buffer(struct comedi_device *dev,
 			       struct comedi_subdevice *s,
-			       struct comedi_async *async, unsigned new_size);
+			       struct comedi_async *async, unsigned new_size)
+{
+	int retval;
+
+	if (new_size > async->max_bufsize)
+		return -EPERM;
+
+	if (s->busy) {
+		DPRINTK("subdevice is busy, cannot resize buffer\n");
+		return -EBUSY;
+	}
+	if (async->mmap_count) {
+		DPRINTK("subdevice is mmapped, cannot resize buffer\n");
+		return -EBUSY;
+	}
+
+	if (!async->prealloc_buf)
+		return -EINVAL;
+
+	/* make sure buffer is an integral number of pages
+	 * (we round up) */
+	new_size = (new_size + PAGE_SIZE - 1) & PAGE_MASK;
+
+	retval = comedi_buf_alloc(dev, s, new_size);
+	if (retval < 0)
+		return retval;
+
+	if (s->buf_change) {
+		retval = s->buf_change(dev, s, new_size);
+		if (retval < 0)
+			return retval;
+	}
+
+	DPRINTK("comedi%i subd %d buffer resized to %i bytes\n",
+		dev->minor, (int)(s - dev->subdevices), async->prealloc_bufsz);
+	return 0;
+}
+
+/* sysfs attribute files */
+
+static const unsigned bytes_per_kibi = 1024;
+
+static ssize_t show_max_read_buffer_kb(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	ssize_t retval;
+	struct comedi_device_file_info *info = dev_get_drvdata(dev);
+	unsigned max_buffer_size_kb = 0;
+	struct comedi_subdevice *const read_subdevice =
+	    comedi_get_read_subdevice(info);
+
+	mutex_lock(&info->device->mutex);
+	if (read_subdevice &&
+	    (read_subdevice->subdev_flags & SDF_CMD_READ) &&
+	    read_subdevice->async) {
+		max_buffer_size_kb = read_subdevice->async->max_bufsize /
+		    bytes_per_kibi;
+	}
+	retval = snprintf(buf, PAGE_SIZE, "%i\n", max_buffer_size_kb);
+	mutex_unlock(&info->device->mutex);
+
+	return retval;
+}
+
+static ssize_t store_max_read_buffer_kb(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct comedi_device_file_info *info = dev_get_drvdata(dev);
+	unsigned int new_max_size_kb;
+	unsigned int new_max_size;
+	int ret;
+	struct comedi_subdevice *const read_subdevice =
+	    comedi_get_read_subdevice(info);
+
+	ret = kstrtouint(buf, 10, &new_max_size_kb);
+	if (ret)
+		return ret;
+	if (new_max_size_kb > (UINT_MAX / bytes_per_kibi))
+		return -EINVAL;
+	new_max_size = new_max_size_kb * bytes_per_kibi;
+
+	mutex_lock(&info->device->mutex);
+	if (read_subdevice == NULL ||
+	    (read_subdevice->subdev_flags & SDF_CMD_READ) == 0 ||
+	    read_subdevice->async == NULL) {
+		mutex_unlock(&info->device->mutex);
+		return -EINVAL;
+	}
+	read_subdevice->async->max_bufsize = new_max_size;
+	mutex_unlock(&info->device->mutex);
+
+	return count;
+}
+
+static DEVICE_ATTR(max_read_buffer_kb, S_IRUGO | S_IWUSR,
+		show_max_read_buffer_kb, store_max_read_buffer_kb);
+
+static ssize_t show_read_buffer_kb(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	ssize_t retval;
+	struct comedi_device_file_info *info = dev_get_drvdata(dev);
+	unsigned buffer_size_kb = 0;
+	struct comedi_subdevice *const read_subdevice =
+	    comedi_get_read_subdevice(info);
+
+	mutex_lock(&info->device->mutex);
+	if (read_subdevice &&
+	    (read_subdevice->subdev_flags & SDF_CMD_READ) &&
+	    read_subdevice->async) {
+		buffer_size_kb = read_subdevice->async->prealloc_bufsz /
+		    bytes_per_kibi;
+	}
+	retval = snprintf(buf, PAGE_SIZE, "%i\n", buffer_size_kb);
+	mutex_unlock(&info->device->mutex);
+
+	return retval;
+}
+
+static ssize_t store_read_buffer_kb(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	struct comedi_device_file_info *info = dev_get_drvdata(dev);
+	unsigned int new_size_kb;
+	unsigned int new_size;
+	int retval;
+	int ret;
+	struct comedi_subdevice *const read_subdevice =
+	    comedi_get_read_subdevice(info);
+
+	ret = kstrtouint(buf, 10, &new_size_kb);
+	if (ret)
+		return ret;
+	if (new_size_kb > (UINT_MAX / bytes_per_kibi))
+		return -EINVAL;
+	new_size = new_size_kb * bytes_per_kibi;
+
+	mutex_lock(&info->device->mutex);
+	if (read_subdevice == NULL ||
+	    (read_subdevice->subdev_flags & SDF_CMD_READ) == 0 ||
+	    read_subdevice->async == NULL) {
+		mutex_unlock(&info->device->mutex);
+		return -EINVAL;
+	}
+	retval = resize_async_buffer(info->device, read_subdevice,
+				     read_subdevice->async, new_size);
+	mutex_unlock(&info->device->mutex);
+
+	if (retval < 0)
+		return retval;
+	return count;
+}
 
-/* declarations for sysfs attribute files */
-static struct device_attribute dev_attr_max_read_buffer_kb;
-static struct device_attribute dev_attr_read_buffer_kb;
-static struct device_attribute dev_attr_max_write_buffer_kb;
-static struct device_attribute dev_attr_write_buffer_kb;
+static DEVICE_ATTR(read_buffer_kb, S_IRUGO | S_IWUSR | S_IWGRP,
+		show_read_buffer_kb, store_read_buffer_kb);
+
+static ssize_t show_max_write_buffer_kb(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	ssize_t retval;
+	struct comedi_device_file_info *info = dev_get_drvdata(dev);
+	unsigned max_buffer_size_kb = 0;
+	struct comedi_subdevice *const write_subdevice =
+	    comedi_get_write_subdevice(info);
+
+	mutex_lock(&info->device->mutex);
+	if (write_subdevice &&
+	    (write_subdevice->subdev_flags & SDF_CMD_WRITE) &&
+	    write_subdevice->async) {
+		max_buffer_size_kb = write_subdevice->async->max_bufsize /
+		    bytes_per_kibi;
+	}
+	retval = snprintf(buf, PAGE_SIZE, "%i\n", max_buffer_size_kb);
+	mutex_unlock(&info->device->mutex);
+
+	return retval;
+}
+
+static ssize_t store_max_write_buffer_kb(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	struct comedi_device_file_info *info = dev_get_drvdata(dev);
+	unsigned int new_max_size_kb;
+	unsigned int new_max_size;
+	int ret;
+	struct comedi_subdevice *const write_subdevice =
+	    comedi_get_write_subdevice(info);
+
+	ret = kstrtouint(buf, 10, &new_max_size_kb);
+	if (ret)
+		return ret;
+	if (new_max_size_kb > (UINT_MAX / bytes_per_kibi))
+		return -EINVAL;
+	new_max_size = new_max_size_kb * bytes_per_kibi;
+
+	mutex_lock(&info->device->mutex);
+	if (write_subdevice == NULL ||
+	    (write_subdevice->subdev_flags & SDF_CMD_WRITE) == 0 ||
+	    write_subdevice->async == NULL) {
+		mutex_unlock(&info->device->mutex);
+		return -EINVAL;
+	}
+	write_subdevice->async->max_bufsize = new_max_size;
+	mutex_unlock(&info->device->mutex);
+
+	return count;
+}
+
+static DEVICE_ATTR(max_write_buffer_kb, S_IRUGO | S_IWUSR,
+		show_max_write_buffer_kb, store_max_write_buffer_kb);
+
+static ssize_t show_write_buffer_kb(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	ssize_t retval;
+	struct comedi_device_file_info *info = dev_get_drvdata(dev);
+	unsigned buffer_size_kb = 0;
+	struct comedi_subdevice *const write_subdevice =
+	    comedi_get_write_subdevice(info);
+
+	mutex_lock(&info->device->mutex);
+	if (write_subdevice &&
+	    (write_subdevice->subdev_flags & SDF_CMD_WRITE) &&
+	    write_subdevice->async) {
+		buffer_size_kb = write_subdevice->async->prealloc_bufsz /
+		    bytes_per_kibi;
+	}
+	retval = snprintf(buf, PAGE_SIZE, "%i\n", buffer_size_kb);
+	mutex_unlock(&info->device->mutex);
+
+	return retval;
+}
+
+static ssize_t store_write_buffer_kb(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct comedi_device_file_info *info = dev_get_drvdata(dev);
+	unsigned int new_size_kb;
+	unsigned int new_size;
+	int retval;
+	int ret;
+	struct comedi_subdevice *const write_subdevice =
+	    comedi_get_write_subdevice(info);
+
+	ret = kstrtouint(buf, 10, &new_size_kb);
+	if (ret)
+		return ret;
+	if (new_size_kb > (UINT_MAX / bytes_per_kibi))
+		return -EINVAL;
+	new_size = ((uint64_t) new_size_kb) * bytes_per_kibi;
+
+	mutex_lock(&info->device->mutex);
+	if (write_subdevice == NULL ||
+	    (write_subdevice->subdev_flags & SDF_CMD_WRITE) == 0 ||
+	    write_subdevice->async == NULL) {
+		mutex_unlock(&info->device->mutex);
+		return -EINVAL;
+	}
+	retval = resize_async_buffer(info->device, write_subdevice,
+				     write_subdevice->async, new_size);
+	mutex_unlock(&info->device->mutex);
+
+	if (retval < 0)
+		return retval;
+	return count;
+}
+
+static DEVICE_ATTR(write_buffer_kb, S_IRUGO | S_IWUSR | S_IWGRP,
+		show_write_buffer_kb, store_write_buffer_kb);
+
+static struct attribute *comedi_attrs[] = {
+	&dev_attr_max_read_buffer_kb.attr,
+	&dev_attr_read_buffer_kb.attr,
+	&dev_attr_max_write_buffer_kb.attr,
+	&dev_attr_write_buffer_kb.attr,
+	NULL
+};
+
+static const struct attribute_group comedi_sysfs_files = {
+	.attrs	= comedi_attrs,
+};
 
 static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
 				  unsigned long arg)
@@ -1937,804 +2217,453 @@ static int comedi_open(struct inode *inode, struct file *file)
 
 	dev->use_count++;
 
-	mutex_unlock(&dev->mutex);
-
-	return 0;
-}
-
-static int comedi_close(struct inode *inode, struct file *file)
-{
-	const unsigned minor = iminor(inode);
-	struct comedi_subdevice *s = NULL;
-	int i;
-	struct comedi_device_file_info *dev_file_info;
-	struct comedi_device *dev;
-	dev_file_info = comedi_get_device_file_info(minor);
-
-	if (dev_file_info == NULL)
-		return -ENODEV;
-	dev = dev_file_info->device;
-	if (dev == NULL)
-		return -ENODEV;
-
-	mutex_lock(&dev->mutex);
-
-	if (dev->subdevices) {
-		for (i = 0; i < dev->n_subdevices; i++) {
-			s = dev->subdevices + i;
-
-			if (s->busy == file)
-				do_cancel(dev, s);
-			if (s->lock == file)
-				s->lock = NULL;
-		}
-	}
-	if (dev->attached && dev->use_count == 1 && dev->close)
-		dev->close(dev);
-
-	module_put(THIS_MODULE);
-	if (dev->attached)
-		module_put(dev->driver->module);
-
-	dev->use_count--;
-
-	mutex_unlock(&dev->mutex);
-
-	if (file->f_flags & FASYNC)
-		comedi_fasync(-1, file, 0);
-
-	return 0;
-}
-
-static int comedi_fasync(int fd, struct file *file, int on)
-{
-	const unsigned minor = iminor(file->f_dentry->d_inode);
-	struct comedi_device_file_info *dev_file_info;
-	struct comedi_device *dev;
-	dev_file_info = comedi_get_device_file_info(minor);
-
-	if (dev_file_info == NULL)
-		return -ENODEV;
-	dev = dev_file_info->device;
-	if (dev == NULL)
-		return -ENODEV;
-
-	return fasync_helper(fd, file, on, &dev->async_queue);
-}
-
-const struct file_operations comedi_fops = {
-	.owner = THIS_MODULE,
-	.unlocked_ioctl = comedi_unlocked_ioctl,
-	.compat_ioctl = comedi_compat_ioctl,
-	.open = comedi_open,
-	.release = comedi_close,
-	.read = comedi_read,
-	.write = comedi_write,
-	.mmap = comedi_mmap,
-	.poll = comedi_poll,
-	.fasync = comedi_fasync,
-	.llseek = noop_llseek,
-};
-
-struct class *comedi_class;
-static struct cdev comedi_cdev;
-
-static void comedi_cleanup_legacy_minors(void)
-{
-	unsigned i;
-
-	for (i = 0; i < comedi_num_legacy_minors; i++)
-		comedi_free_board_minor(i);
-}
-
-static int __init comedi_init(void)
-{
-	int i;
-	int retval;
-
-	printk(KERN_INFO "comedi: version " COMEDI_RELEASE
-	       " - http://www.comedi.org\n");
-
-	if (comedi_num_legacy_minors < 0 ||
-	    comedi_num_legacy_minors > COMEDI_NUM_BOARD_MINORS) {
-		printk(KERN_ERR "comedi: error: invalid value for module "
-		       "parameter \"comedi_num_legacy_minors\".  Valid values "
-		       "are 0 through %i.\n", COMEDI_NUM_BOARD_MINORS);
-		return -EINVAL;
-	}
-
-	/*
-	 * comedi is unusable if both comedi_autoconfig and
-	 * comedi_num_legacy_minors are zero, so we might as well adjust the
-	 * defaults in that case
-	 */
-	if (comedi_autoconfig == 0 && comedi_num_legacy_minors == 0)
-		comedi_num_legacy_minors = 16;
-
-	memset(comedi_file_info_table, 0,
-	       sizeof(struct comedi_device_file_info *) * COMEDI_NUM_MINORS);
-
-	retval = register_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
-					COMEDI_NUM_MINORS, "comedi");
-	if (retval)
-		return -EIO;
-	cdev_init(&comedi_cdev, &comedi_fops);
-	comedi_cdev.owner = THIS_MODULE;
-	kobject_set_name(&comedi_cdev.kobj, "comedi");
-	if (cdev_add(&comedi_cdev, MKDEV(COMEDI_MAJOR, 0), COMEDI_NUM_MINORS)) {
-		unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
-					 COMEDI_NUM_MINORS);
-		return -EIO;
-	}
-	comedi_class = class_create(THIS_MODULE, "comedi");
-	if (IS_ERR(comedi_class)) {
-		printk(KERN_ERR "comedi: failed to create class");
-		cdev_del(&comedi_cdev);
-		unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
-					 COMEDI_NUM_MINORS);
-		return PTR_ERR(comedi_class);
-	}
-
-	/* XXX requires /proc interface */
-	comedi_proc_init();
-
-	/* create devices files for legacy/manual use */
-	for (i = 0; i < comedi_num_legacy_minors; i++) {
-		int minor;
-		minor = comedi_alloc_board_minor(NULL);
-		if (minor < 0) {
-			comedi_cleanup_legacy_minors();
-			cdev_del(&comedi_cdev);
-			unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
-						 COMEDI_NUM_MINORS);
-			return minor;
-		}
-	}
-
-	return 0;
-}
-
-static void __exit comedi_cleanup(void)
-{
-	int i;
-
-	comedi_cleanup_legacy_minors();
-	for (i = 0; i < COMEDI_NUM_MINORS; ++i)
-		BUG_ON(comedi_file_info_table[i]);
-
-	class_destroy(comedi_class);
-	cdev_del(&comedi_cdev);
-	unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0), COMEDI_NUM_MINORS);
-
-	comedi_proc_cleanup();
-}
-
-module_init(comedi_init);
-module_exit(comedi_cleanup);
-
-void comedi_error(const struct comedi_device *dev, const char *s)
-{
-	printk(KERN_ERR "comedi%d: %s: %s\n", dev->minor,
-	       dev->driver->driver_name, s);
-}
-EXPORT_SYMBOL(comedi_error);
-
-void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s)
-{
-	struct comedi_async *async = s->async;
-	unsigned runflags = 0;
-	unsigned runflags_mask = 0;
-
-	/* DPRINTK("comedi_event 0x%x\n",mask); */
-
-	if ((comedi_get_subdevice_runflags(s) & SRF_RUNNING) == 0)
-		return;
-
-	if (s->
-	    async->events & (COMEDI_CB_EOA | COMEDI_CB_ERROR |
-			     COMEDI_CB_OVERFLOW)) {
-		runflags_mask |= SRF_RUNNING;
-	}
-	/* remember if an error event has occurred, so an error
-	 * can be returned the next time the user does a read() */
-	if (s->async->events & (COMEDI_CB_ERROR | COMEDI_CB_OVERFLOW)) {
-		runflags_mask |= SRF_ERROR;
-		runflags |= SRF_ERROR;
-	}
-	if (runflags_mask) {
-		/*sets SRF_ERROR and SRF_RUNNING together atomically */
-		comedi_set_subdevice_runflags(s, runflags_mask, runflags);
-	}
-
-	if (async->cb_mask & s->async->events) {
-		if (comedi_get_subdevice_runflags(s) & SRF_USER) {
-			wake_up_interruptible(&async->wait_head);
-			if (s->subdev_flags & SDF_CMD_READ)
-				kill_fasync(&dev->async_queue, SIGIO, POLL_IN);
-			if (s->subdev_flags & SDF_CMD_WRITE)
-				kill_fasync(&dev->async_queue, SIGIO, POLL_OUT);
-		} else {
-			if (async->cb_func)
-				async->cb_func(s->async->events, async->cb_arg);
-		}
-	}
-	s->async->events = 0;
-}
-EXPORT_SYMBOL(comedi_event);
-
-unsigned comedi_get_subdevice_runflags(struct comedi_subdevice *s)
-{
-	unsigned long flags;
-	unsigned runflags;
+	mutex_unlock(&dev->mutex);
 
-	spin_lock_irqsave(&s->spin_lock, flags);
-	runflags = s->runflags;
-	spin_unlock_irqrestore(&s->spin_lock, flags);
-	return runflags;
+	return 0;
 }
-EXPORT_SYMBOL(comedi_get_subdevice_runflags);
 
-static int is_device_busy(struct comedi_device *dev)
+static int comedi_close(struct inode *inode, struct file *file)
 {
-	struct comedi_subdevice *s;
+	const unsigned minor = iminor(inode);
+	struct comedi_subdevice *s = NULL;
 	int i;
+	struct comedi_device_file_info *dev_file_info;
+	struct comedi_device *dev;
+	dev_file_info = comedi_get_device_file_info(minor);
 
-	if (!dev->attached)
-		return 0;
+	if (dev_file_info == NULL)
+		return -ENODEV;
+	dev = dev_file_info->device;
+	if (dev == NULL)
+		return -ENODEV;
 
-	for (i = 0; i < dev->n_subdevices; i++) {
-		s = dev->subdevices + i;
-		if (s->busy)
-			return 1;
-		if (s->async && s->async->mmap_count)
-			return 1;
+	mutex_lock(&dev->mutex);
+
+	if (dev->subdevices) {
+		for (i = 0; i < dev->n_subdevices; i++) {
+			s = dev->subdevices + i;
+
+			if (s->busy == file)
+				do_cancel(dev, s);
+			if (s->lock == file)
+				s->lock = NULL;
+		}
 	}
+	if (dev->attached && dev->use_count == 1 && dev->close)
+		dev->close(dev);
+
+	module_put(THIS_MODULE);
+	if (dev->attached)
+		module_put(dev->driver->module);
+
+	dev->use_count--;
+
+	mutex_unlock(&dev->mutex);
+
+	if (file->f_flags & FASYNC)
+		comedi_fasync(-1, file, 0);
 
 	return 0;
 }
 
-static void comedi_device_init(struct comedi_device *dev)
+static int comedi_fasync(int fd, struct file *file, int on)
 {
-	memset(dev, 0, sizeof(struct comedi_device));
-	spin_lock_init(&dev->spinlock);
-	mutex_init(&dev->mutex);
-	dev->minor = -1;
-}
+	const unsigned minor = iminor(file->f_dentry->d_inode);
+	struct comedi_device_file_info *dev_file_info;
+	struct comedi_device *dev;
+	dev_file_info = comedi_get_device_file_info(minor);
 
-static void comedi_device_cleanup(struct comedi_device *dev)
-{
+	if (dev_file_info == NULL)
+		return -ENODEV;
+	dev = dev_file_info->device;
 	if (dev == NULL)
-		return;
-	mutex_lock(&dev->mutex);
-	comedi_device_detach(dev);
-	mutex_unlock(&dev->mutex);
-	mutex_destroy(&dev->mutex);
+		return -ENODEV;
+
+	return fasync_helper(fd, file, on, &dev->async_queue);
 }
 
-int comedi_alloc_board_minor(struct device *hardware_device)
+const struct file_operations comedi_fops = {
+	.owner = THIS_MODULE,
+	.unlocked_ioctl = comedi_unlocked_ioctl,
+	.compat_ioctl = comedi_compat_ioctl,
+	.open = comedi_open,
+	.release = comedi_close,
+	.read = comedi_read,
+	.write = comedi_write,
+	.mmap = comedi_mmap,
+	.poll = comedi_poll,
+	.fasync = comedi_fasync,
+	.llseek = noop_llseek,
+};
+
+struct class *comedi_class;
+static struct cdev comedi_cdev;
+
+static void comedi_cleanup_legacy_minors(void)
 {
-	struct comedi_device_file_info *info;
-	struct device *csdev;
 	unsigned i;
-	int retval;
 
-	info = kzalloc(sizeof(struct comedi_device_file_info), GFP_KERNEL);
-	if (info == NULL)
-		return -ENOMEM;
-	info->device = kzalloc(sizeof(struct comedi_device), GFP_KERNEL);
-	if (info->device == NULL) {
-		kfree(info);
-		return -ENOMEM;
-	}
-	info->hardware_device = hardware_device;
-	comedi_device_init(info->device);
-	spin_lock(&comedi_file_info_table_lock);
-	for (i = 0; i < COMEDI_NUM_BOARD_MINORS; ++i) {
-		if (comedi_file_info_table[i] == NULL) {
-			comedi_file_info_table[i] = info;
-			break;
-		}
-	}
-	spin_unlock(&comedi_file_info_table_lock);
-	if (i == COMEDI_NUM_BOARD_MINORS) {
-		comedi_device_cleanup(info->device);
-		kfree(info->device);
-		kfree(info);
-		printk(KERN_ERR
-		       "comedi: error: "
-		       "ran out of minor numbers for board device files.\n");
-		return -EBUSY;
-	}
-	info->device->minor = i;
-	csdev = device_create(comedi_class, hardware_device,
-			      MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i", i);
-	if (!IS_ERR(csdev))
-		info->device->class_dev = csdev;
-	dev_set_drvdata(csdev, info);
-	retval = device_create_file(csdev, &dev_attr_max_read_buffer_kb);
-	if (retval) {
-		printk(KERN_ERR
-		       "comedi: "
-		       "failed to create sysfs attribute file \"%s\".\n",
-		       dev_attr_max_read_buffer_kb.attr.name);
-		comedi_free_board_minor(i);
-		return retval;
-	}
-	retval = device_create_file(csdev, &dev_attr_read_buffer_kb);
-	if (retval) {
-		printk(KERN_ERR
-		       "comedi: "
-		       "failed to create sysfs attribute file \"%s\".\n",
-		       dev_attr_read_buffer_kb.attr.name);
-		comedi_free_board_minor(i);
-		return retval;
-	}
-	retval = device_create_file(csdev, &dev_attr_max_write_buffer_kb);
-	if (retval) {
-		printk(KERN_ERR
-		       "comedi: "
-		       "failed to create sysfs attribute file \"%s\".\n",
-		       dev_attr_max_write_buffer_kb.attr.name);
-		comedi_free_board_minor(i);
-		return retval;
-	}
-	retval = device_create_file(csdev, &dev_attr_write_buffer_kb);
-	if (retval) {
-		printk(KERN_ERR
-		       "comedi: "
-		       "failed to create sysfs attribute file \"%s\".\n",
-		       dev_attr_write_buffer_kb.attr.name);
+	for (i = 0; i < comedi_num_legacy_minors; i++)
 		comedi_free_board_minor(i);
-		return retval;
-	}
-	return i;
 }
 
-void comedi_free_board_minor(unsigned minor)
+static int __init comedi_init(void)
 {
-	struct comedi_device_file_info *info;
+	int i;
+	int retval;
 
-	BUG_ON(minor >= COMEDI_NUM_BOARD_MINORS);
-	spin_lock(&comedi_file_info_table_lock);
-	info = comedi_file_info_table[minor];
-	comedi_file_info_table[minor] = NULL;
-	spin_unlock(&comedi_file_info_table_lock);
+	printk(KERN_INFO "comedi: version " COMEDI_RELEASE
+	       " - http://www.comedi.org\n");
 
-	if (info) {
-		struct comedi_device *dev = info->device;
-		if (dev) {
-			if (dev->class_dev) {
-				device_destroy(comedi_class,
-					       MKDEV(COMEDI_MAJOR, dev->minor));
-			}
-			comedi_device_cleanup(dev);
-			kfree(dev);
-		}
-		kfree(info);
+	if (comedi_num_legacy_minors < 0 ||
+	    comedi_num_legacy_minors > COMEDI_NUM_BOARD_MINORS) {
+		printk(KERN_ERR "comedi: error: invalid value for module "
+		       "parameter \"comedi_num_legacy_minors\".  Valid values "
+		       "are 0 through %i.\n", COMEDI_NUM_BOARD_MINORS);
+		return -EINVAL;
 	}
-}
-
-int comedi_find_board_minor(struct device *hardware_device)
-{
-	int minor;
-	struct comedi_device_file_info *info;
 
-	for (minor = 0; minor < COMEDI_NUM_BOARD_MINORS; minor++) {
-		spin_lock(&comedi_file_info_table_lock);
-		info = comedi_file_info_table[minor];
-		if (info && info->hardware_device == hardware_device) {
-			spin_unlock(&comedi_file_info_table_lock);
-			return minor;
-		}
-		spin_unlock(&comedi_file_info_table_lock);
-	}
-	return -ENODEV;
-}
+	/*
+	 * comedi is unusable if both comedi_autoconfig and
+	 * comedi_num_legacy_minors are zero, so we might as well adjust the
+	 * defaults in that case
+	 */
+	if (comedi_autoconfig == 0 && comedi_num_legacy_minors == 0)
+		comedi_num_legacy_minors = 16;
 
-int comedi_alloc_subdevice_minor(struct comedi_device *dev,
-				 struct comedi_subdevice *s)
-{
-	struct comedi_device_file_info *info;
-	struct device *csdev;
-	unsigned i;
-	int retval;
+	memset(comedi_file_info_table, 0,
+	       sizeof(struct comedi_device_file_info *) * COMEDI_NUM_MINORS);
 
-	info = kmalloc(sizeof(struct comedi_device_file_info), GFP_KERNEL);
-	if (info == NULL)
-		return -ENOMEM;
-	info->device = dev;
-	info->read_subdevice = s;
-	info->write_subdevice = s;
-	spin_lock(&comedi_file_info_table_lock);
-	for (i = COMEDI_FIRST_SUBDEVICE_MINOR; i < COMEDI_NUM_MINORS; ++i) {
-		if (comedi_file_info_table[i] == NULL) {
-			comedi_file_info_table[i] = info;
-			break;
-		}
-	}
-	spin_unlock(&comedi_file_info_table_lock);
-	if (i == COMEDI_NUM_MINORS) {
-		kfree(info);
-		printk(KERN_ERR
-		       "comedi: error: "
-		       "ran out of minor numbers for board device files.\n");
-		return -EBUSY;
-	}
-	s->minor = i;
-	csdev = device_create(comedi_class, dev->class_dev,
-			      MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i_subd%i",
-			      dev->minor, (int)(s - dev->subdevices));
-	if (!IS_ERR(csdev))
-		s->class_dev = csdev;
-	dev_set_drvdata(csdev, info);
-	retval = device_create_file(csdev, &dev_attr_max_read_buffer_kb);
-	if (retval) {
-		printk(KERN_ERR
-		       "comedi: "
-		       "failed to create sysfs attribute file \"%s\".\n",
-		       dev_attr_max_read_buffer_kb.attr.name);
-		comedi_free_subdevice_minor(s);
-		return retval;
-	}
-	retval = device_create_file(csdev, &dev_attr_read_buffer_kb);
-	if (retval) {
-		printk(KERN_ERR
-		       "comedi: "
-		       "failed to create sysfs attribute file \"%s\".\n",
-		       dev_attr_read_buffer_kb.attr.name);
-		comedi_free_subdevice_minor(s);
-		return retval;
+	retval = register_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
+					COMEDI_NUM_MINORS, "comedi");
+	if (retval)
+		return -EIO;
+	cdev_init(&comedi_cdev, &comedi_fops);
+	comedi_cdev.owner = THIS_MODULE;
+	kobject_set_name(&comedi_cdev.kobj, "comedi");
+	if (cdev_add(&comedi_cdev, MKDEV(COMEDI_MAJOR, 0), COMEDI_NUM_MINORS)) {
+		unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
+					 COMEDI_NUM_MINORS);
+		return -EIO;
 	}
-	retval = device_create_file(csdev, &dev_attr_max_write_buffer_kb);
-	if (retval) {
-		printk(KERN_ERR
-		       "comedi: "
-		       "failed to create sysfs attribute file \"%s\".\n",
-		       dev_attr_max_write_buffer_kb.attr.name);
-		comedi_free_subdevice_minor(s);
-		return retval;
+	comedi_class = class_create(THIS_MODULE, "comedi");
+	if (IS_ERR(comedi_class)) {
+		printk(KERN_ERR "comedi: failed to create class");
+		cdev_del(&comedi_cdev);
+		unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
+					 COMEDI_NUM_MINORS);
+		return PTR_ERR(comedi_class);
 	}
-	retval = device_create_file(csdev, &dev_attr_write_buffer_kb);
-	if (retval) {
-		printk(KERN_ERR
-		       "comedi: "
-		       "failed to create sysfs attribute file \"%s\".\n",
-		       dev_attr_write_buffer_kb.attr.name);
-		comedi_free_subdevice_minor(s);
-		return retval;
+
+	/* XXX requires /proc interface */
+	comedi_proc_init();
+
+	/* create devices files for legacy/manual use */
+	for (i = 0; i < comedi_num_legacy_minors; i++) {
+		int minor;
+		minor = comedi_alloc_board_minor(NULL);
+		if (minor < 0) {
+			comedi_cleanup_legacy_minors();
+			cdev_del(&comedi_cdev);
+			unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0),
+						 COMEDI_NUM_MINORS);
+			return minor;
+		}
 	}
-	return i;
+
+	return 0;
 }
 
-void comedi_free_subdevice_minor(struct comedi_subdevice *s)
+static void __exit comedi_cleanup(void)
 {
-	struct comedi_device_file_info *info;
-
-	if (s == NULL)
-		return;
-	if (s->minor < 0)
-		return;
+	int i;
 
-	BUG_ON(s->minor >= COMEDI_NUM_MINORS);
-	BUG_ON(s->minor < COMEDI_FIRST_SUBDEVICE_MINOR);
+	comedi_cleanup_legacy_minors();
+	for (i = 0; i < COMEDI_NUM_MINORS; ++i)
+		BUG_ON(comedi_file_info_table[i]);
 
-	spin_lock(&comedi_file_info_table_lock);
-	info = comedi_file_info_table[s->minor];
-	comedi_file_info_table[s->minor] = NULL;
-	spin_unlock(&comedi_file_info_table_lock);
+	class_destroy(comedi_class);
+	cdev_del(&comedi_cdev);
+	unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0), COMEDI_NUM_MINORS);
 
-	if (s->class_dev) {
-		device_destroy(comedi_class, MKDEV(COMEDI_MAJOR, s->minor));
-		s->class_dev = NULL;
-	}
-	kfree(info);
+	comedi_proc_cleanup();
 }
 
-struct comedi_device_file_info *comedi_get_device_file_info(unsigned minor)
-{
-	struct comedi_device_file_info *info;
+module_init(comedi_init);
+module_exit(comedi_cleanup);
 
-	BUG_ON(minor >= COMEDI_NUM_MINORS);
-	spin_lock(&comedi_file_info_table_lock);
-	info = comedi_file_info_table[minor];
-	spin_unlock(&comedi_file_info_table_lock);
-	return info;
+void comedi_error(const struct comedi_device *dev, const char *s)
+{
+	printk(KERN_ERR "comedi%d: %s: %s\n", dev->minor,
+	       dev->driver->driver_name, s);
 }
-EXPORT_SYMBOL_GPL(comedi_get_device_file_info);
+EXPORT_SYMBOL(comedi_error);
 
-static int resize_async_buffer(struct comedi_device *dev,
-			       struct comedi_subdevice *s,
-			       struct comedi_async *async, unsigned new_size)
+void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s)
 {
-	int retval;
+	struct comedi_async *async = s->async;
+	unsigned runflags = 0;
+	unsigned runflags_mask = 0;
 
-	if (new_size > async->max_bufsize)
-		return -EPERM;
+	/* DPRINTK("comedi_event 0x%x\n",mask); */
 
-	if (s->busy) {
-		DPRINTK("subdevice is busy, cannot resize buffer\n");
-		return -EBUSY;
+	if ((comedi_get_subdevice_runflags(s) & SRF_RUNNING) == 0)
+		return;
+
+	if (s->
+	    async->events & (COMEDI_CB_EOA | COMEDI_CB_ERROR |
+			     COMEDI_CB_OVERFLOW)) {
+		runflags_mask |= SRF_RUNNING;
 	}
-	if (async->mmap_count) {
-		DPRINTK("subdevice is mmapped, cannot resize buffer\n");
-		return -EBUSY;
+	/* remember if an error event has occurred, so an error
+	 * can be returned the next time the user does a read() */
+	if (s->async->events & (COMEDI_CB_ERROR | COMEDI_CB_OVERFLOW)) {
+		runflags_mask |= SRF_ERROR;
+		runflags |= SRF_ERROR;
 	}
-
-	if (!async->prealloc_buf)
-		return -EINVAL;
-
-	/* make sure buffer is an integral number of pages
-	 * (we round up) */
-	new_size = (new_size + PAGE_SIZE - 1) & PAGE_MASK;
-
-	retval = comedi_buf_alloc(dev, s, new_size);
-	if (retval < 0)
-		return retval;
-
-	if (s->buf_change) {
-		retval = s->buf_change(dev, s, new_size);
-		if (retval < 0)
-			return retval;
+	if (runflags_mask) {
+		/*sets SRF_ERROR and SRF_RUNNING together atomically */
+		comedi_set_subdevice_runflags(s, runflags_mask, runflags);
 	}
 
-	DPRINTK("comedi%i subd %d buffer resized to %i bytes\n",
-		dev->minor, (int)(s - dev->subdevices), async->prealloc_bufsz);
-	return 0;
+	if (async->cb_mask & s->async->events) {
+		if (comedi_get_subdevice_runflags(s) & SRF_USER) {
+			wake_up_interruptible(&async->wait_head);
+			if (s->subdev_flags & SDF_CMD_READ)
+				kill_fasync(&dev->async_queue, SIGIO, POLL_IN);
+			if (s->subdev_flags & SDF_CMD_WRITE)
+				kill_fasync(&dev->async_queue, SIGIO, POLL_OUT);
+		} else {
+			if (async->cb_func)
+				async->cb_func(s->async->events, async->cb_arg);
+		}
+	}
+	s->async->events = 0;
 }
+EXPORT_SYMBOL(comedi_event);
 
-/* sysfs attribute files */
-
-static const unsigned bytes_per_kibi = 1024;
-
-static ssize_t show_max_read_buffer_kb(struct device *dev,
-				       struct device_attribute *attr, char *buf)
+unsigned comedi_get_subdevice_runflags(struct comedi_subdevice *s)
 {
-	ssize_t retval;
-	struct comedi_device_file_info *info = dev_get_drvdata(dev);
-	unsigned max_buffer_size_kb = 0;
-	struct comedi_subdevice *const read_subdevice =
-	    comedi_get_read_subdevice(info);
-
-	mutex_lock(&info->device->mutex);
-	if (read_subdevice &&
-	    (read_subdevice->subdev_flags & SDF_CMD_READ) &&
-	    read_subdevice->async) {
-		max_buffer_size_kb = read_subdevice->async->max_bufsize /
-		    bytes_per_kibi;
-	}
-	retval = snprintf(buf, PAGE_SIZE, "%i\n", max_buffer_size_kb);
-	mutex_unlock(&info->device->mutex);
+	unsigned long flags;
+	unsigned runflags;
 
-	return retval;
+	spin_lock_irqsave(&s->spin_lock, flags);
+	runflags = s->runflags;
+	spin_unlock_irqrestore(&s->spin_lock, flags);
+	return runflags;
 }
+EXPORT_SYMBOL(comedi_get_subdevice_runflags);
 
-static ssize_t store_max_read_buffer_kb(struct device *dev,
-					struct device_attribute *attr,
-					const char *buf, size_t count)
+static int is_device_busy(struct comedi_device *dev)
 {
-	struct comedi_device_file_info *info = dev_get_drvdata(dev);
-	unsigned int new_max_size_kb;
-	unsigned int new_max_size;
-	int ret;
-	struct comedi_subdevice *const read_subdevice =
-	    comedi_get_read_subdevice(info);
+	struct comedi_subdevice *s;
+	int i;
 
-	ret = kstrtouint(buf, 10, &new_max_size_kb);
-	if (ret)
-		return ret;
-	if (new_max_size_kb > (UINT_MAX / bytes_per_kibi))
-		return -EINVAL;
-	new_max_size = new_max_size_kb * bytes_per_kibi;
+	if (!dev->attached)
+		return 0;
 
-	mutex_lock(&info->device->mutex);
-	if (read_subdevice == NULL ||
-	    (read_subdevice->subdev_flags & SDF_CMD_READ) == 0 ||
-	    read_subdevice->async == NULL) {
-		mutex_unlock(&info->device->mutex);
-		return -EINVAL;
+	for (i = 0; i < dev->n_subdevices; i++) {
+		s = dev->subdevices + i;
+		if (s->busy)
+			return 1;
+		if (s->async && s->async->mmap_count)
+			return 1;
 	}
-	read_subdevice->async->max_bufsize = new_max_size;
-	mutex_unlock(&info->device->mutex);
 
-	return count;
+	return 0;
 }
 
-static struct device_attribute dev_attr_max_read_buffer_kb = {
-	.attr = {
-		 .name = "max_read_buffer_kb",
-		 .mode = S_IRUGO | S_IWUSR},
-	.show = &show_max_read_buffer_kb,
-	.store = &store_max_read_buffer_kb
-};
+static void comedi_device_init(struct comedi_device *dev)
+{
+	memset(dev, 0, sizeof(struct comedi_device));
+	spin_lock_init(&dev->spinlock);
+	mutex_init(&dev->mutex);
+	dev->minor = -1;
+}
 
-static ssize_t show_read_buffer_kb(struct device *dev,
-				   struct device_attribute *attr, char *buf)
+static void comedi_device_cleanup(struct comedi_device *dev)
 {
-	ssize_t retval;
-	struct comedi_device_file_info *info = dev_get_drvdata(dev);
-	unsigned buffer_size_kb = 0;
-	struct comedi_subdevice *const read_subdevice =
-	    comedi_get_read_subdevice(info);
+	if (dev == NULL)
+		return;
+	mutex_lock(&dev->mutex);
+	comedi_device_detach(dev);
+	mutex_unlock(&dev->mutex);
+	mutex_destroy(&dev->mutex);
+}
+
+int comedi_alloc_board_minor(struct device *hardware_device)
+{
+	struct comedi_device_file_info *info;
+	struct device *csdev;
+	unsigned i;
+	int retval;
+
+	info = kzalloc(sizeof(struct comedi_device_file_info), GFP_KERNEL);
+	if (info == NULL)
+		return -ENOMEM;
+	info->device = kzalloc(sizeof(struct comedi_device), GFP_KERNEL);
+	if (info->device == NULL) {
+		kfree(info);
+		return -ENOMEM;
+	}
+	info->hardware_device = hardware_device;
+	comedi_device_init(info->device);
+	spin_lock(&comedi_file_info_table_lock);
+	for (i = 0; i < COMEDI_NUM_BOARD_MINORS; ++i) {
+		if (comedi_file_info_table[i] == NULL) {
+			comedi_file_info_table[i] = info;
+			break;
+		}
+	}
+	spin_unlock(&comedi_file_info_table_lock);
+	if (i == COMEDI_NUM_BOARD_MINORS) {
+		comedi_device_cleanup(info->device);
+		kfree(info->device);
+		kfree(info);
+		printk(KERN_ERR
+		       "comedi: error: "
+		       "ran out of minor numbers for board device files.\n");
+		return -EBUSY;
+	}
+	info->device->minor = i;
+	csdev = device_create(comedi_class, hardware_device,
+			      MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i", i);
+	if (!IS_ERR(csdev))
+		info->device->class_dev = csdev;
+	dev_set_drvdata(csdev, info);
 
-	mutex_lock(&info->device->mutex);
-	if (read_subdevice &&
-	    (read_subdevice->subdev_flags & SDF_CMD_READ) &&
-	    read_subdevice->async) {
-		buffer_size_kb = read_subdevice->async->prealloc_bufsz /
-		    bytes_per_kibi;
+	retval = sysfs_create_group(&csdev->kobj, &comedi_sysfs_files);
+	if (retval) {
+		printk(KERN_ERR
+		       "comedi: failed to create sysfs attribute files\n");
+		comedi_free_board_minor(i);
+		return retval;
 	}
-	retval = snprintf(buf, PAGE_SIZE, "%i\n", buffer_size_kb);
-	mutex_unlock(&info->device->mutex);
 
-	return retval;
+	return i;
 }
 
-static ssize_t store_read_buffer_kb(struct device *dev,
-				    struct device_attribute *attr,
-				    const char *buf, size_t count)
+void comedi_free_board_minor(unsigned minor)
 {
-	struct comedi_device_file_info *info = dev_get_drvdata(dev);
-	unsigned int new_size_kb;
-	unsigned int new_size;
-	int retval;
-	int ret;
-	struct comedi_subdevice *const read_subdevice =
-	    comedi_get_read_subdevice(info);
+	struct comedi_device_file_info *info;
 
-	ret = kstrtouint(buf, 10, &new_size_kb);
-	if (ret)
-		return ret;
-	if (new_size_kb > (UINT_MAX / bytes_per_kibi))
-		return -EINVAL;
-	new_size = new_size_kb * bytes_per_kibi;
+	BUG_ON(minor >= COMEDI_NUM_BOARD_MINORS);
+	spin_lock(&comedi_file_info_table_lock);
+	info = comedi_file_info_table[minor];
+	comedi_file_info_table[minor] = NULL;
+	spin_unlock(&comedi_file_info_table_lock);
 
-	mutex_lock(&info->device->mutex);
-	if (read_subdevice == NULL ||
-	    (read_subdevice->subdev_flags & SDF_CMD_READ) == 0 ||
-	    read_subdevice->async == NULL) {
-		mutex_unlock(&info->device->mutex);
-		return -EINVAL;
+	if (info) {
+		struct comedi_device *dev = info->device;
+		if (dev) {
+			if (dev->class_dev) {
+				device_destroy(comedi_class,
+					       MKDEV(COMEDI_MAJOR, dev->minor));
+			}
+			comedi_device_cleanup(dev);
+			kfree(dev);
+		}
+		kfree(info);
 	}
-	retval = resize_async_buffer(info->device, read_subdevice,
-				     read_subdevice->async, new_size);
-	mutex_unlock(&info->device->mutex);
-
-	if (retval < 0)
-		return retval;
-	return count;
 }
 
-static struct device_attribute dev_attr_read_buffer_kb = {
-	.attr = {
-		 .name = "read_buffer_kb",
-		 .mode = S_IRUGO | S_IWUSR | S_IWGRP},
-	.show = &show_read_buffer_kb,
-	.store = &store_read_buffer_kb
-};
-
-static ssize_t show_max_write_buffer_kb(struct device *dev,
-					struct device_attribute *attr,
-					char *buf)
+int comedi_find_board_minor(struct device *hardware_device)
 {
-	ssize_t retval;
-	struct comedi_device_file_info *info = dev_get_drvdata(dev);
-	unsigned max_buffer_size_kb = 0;
-	struct comedi_subdevice *const write_subdevice =
-	    comedi_get_write_subdevice(info);
+	int minor;
+	struct comedi_device_file_info *info;
 
-	mutex_lock(&info->device->mutex);
-	if (write_subdevice &&
-	    (write_subdevice->subdev_flags & SDF_CMD_WRITE) &&
-	    write_subdevice->async) {
-		max_buffer_size_kb = write_subdevice->async->max_bufsize /
-		    bytes_per_kibi;
+	for (minor = 0; minor < COMEDI_NUM_BOARD_MINORS; minor++) {
+		spin_lock(&comedi_file_info_table_lock);
+		info = comedi_file_info_table[minor];
+		if (info && info->hardware_device == hardware_device) {
+			spin_unlock(&comedi_file_info_table_lock);
+			return minor;
+		}
+		spin_unlock(&comedi_file_info_table_lock);
 	}
-	retval = snprintf(buf, PAGE_SIZE, "%i\n", max_buffer_size_kb);
-	mutex_unlock(&info->device->mutex);
-
-	return retval;
+	return -ENODEV;
 }
 
-static ssize_t store_max_write_buffer_kb(struct device *dev,
-					 struct device_attribute *attr,
-					 const char *buf, size_t count)
+int comedi_alloc_subdevice_minor(struct comedi_device *dev,
+				 struct comedi_subdevice *s)
 {
-	struct comedi_device_file_info *info = dev_get_drvdata(dev);
-	unsigned int new_max_size_kb;
-	unsigned int new_max_size;
-	int ret;
-	struct comedi_subdevice *const write_subdevice =
-	    comedi_get_write_subdevice(info);
+	struct comedi_device_file_info *info;
+	struct device *csdev;
+	unsigned i;
+	int retval;
 
-	ret = kstrtouint(buf, 10, &new_max_size_kb);
-	if (ret)
-		return ret;
-	if (new_max_size_kb > (UINT_MAX / bytes_per_kibi))
-		return -EINVAL;
-	new_max_size = new_max_size_kb * bytes_per_kibi;
+	info = kmalloc(sizeof(struct comedi_device_file_info), GFP_KERNEL);
+	if (info == NULL)
+		return -ENOMEM;
+	info->device = dev;
+	info->read_subdevice = s;
+	info->write_subdevice = s;
+	spin_lock(&comedi_file_info_table_lock);
+	for (i = COMEDI_FIRST_SUBDEVICE_MINOR; i < COMEDI_NUM_MINORS; ++i) {
+		if (comedi_file_info_table[i] == NULL) {
+			comedi_file_info_table[i] = info;
+			break;
+		}
+	}
+	spin_unlock(&comedi_file_info_table_lock);
+	if (i == COMEDI_NUM_MINORS) {
+		kfree(info);
+		printk(KERN_ERR
+		       "comedi: error: "
+		       "ran out of minor numbers for board device files.\n");
+		return -EBUSY;
+	}
+	s->minor = i;
+	csdev = device_create(comedi_class, dev->class_dev,
+			      MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i_subd%i",
+			      dev->minor, (int)(s - dev->subdevices));
+	if (!IS_ERR(csdev))
+		s->class_dev = csdev;
+	dev_set_drvdata(csdev, info);
 
-	mutex_lock(&info->device->mutex);
-	if (write_subdevice == NULL ||
-	    (write_subdevice->subdev_flags & SDF_CMD_WRITE) == 0 ||
-	    write_subdevice->async == NULL) {
-		mutex_unlock(&info->device->mutex);
-		return -EINVAL;
+	retval = sysfs_create_group(&csdev->kobj, &comedi_sysfs_files);
+	if (retval) {
+		printk(KERN_ERR
+		       "comedi: failed to create sysfs attribute files\n");
+		comedi_free_subdevice_minor(s);
+		return retval;
 	}
-	write_subdevice->async->max_bufsize = new_max_size;
-	mutex_unlock(&info->device->mutex);
 
-	return count;
+	return i;
 }
 
-static struct device_attribute dev_attr_max_write_buffer_kb = {
-	.attr = {
-		 .name = "max_write_buffer_kb",
-		 .mode = S_IRUGO | S_IWUSR},
-	.show = &show_max_write_buffer_kb,
-	.store = &store_max_write_buffer_kb
-};
-
-static ssize_t show_write_buffer_kb(struct device *dev,
-				    struct device_attribute *attr, char *buf)
+void comedi_free_subdevice_minor(struct comedi_subdevice *s)
 {
-	ssize_t retval;
-	struct comedi_device_file_info *info = dev_get_drvdata(dev);
-	unsigned buffer_size_kb = 0;
-	struct comedi_subdevice *const write_subdevice =
-	    comedi_get_write_subdevice(info);
-
-	mutex_lock(&info->device->mutex);
-	if (write_subdevice &&
-	    (write_subdevice->subdev_flags & SDF_CMD_WRITE) &&
-	    write_subdevice->async) {
-		buffer_size_kb = write_subdevice->async->prealloc_bufsz /
-		    bytes_per_kibi;
-	}
-	retval = snprintf(buf, PAGE_SIZE, "%i\n", buffer_size_kb);
-	mutex_unlock(&info->device->mutex);
+	struct comedi_device_file_info *info;
 
-	return retval;
-}
+	if (s == NULL)
+		return;
+	if (s->minor < 0)
+		return;
 
-static ssize_t store_write_buffer_kb(struct device *dev,
-				     struct device_attribute *attr,
-				     const char *buf, size_t count)
-{
-	struct comedi_device_file_info *info = dev_get_drvdata(dev);
-	unsigned int new_size_kb;
-	unsigned int new_size;
-	int retval;
-	int ret;
-	struct comedi_subdevice *const write_subdevice =
-	    comedi_get_write_subdevice(info);
+	BUG_ON(s->minor >= COMEDI_NUM_MINORS);
+	BUG_ON(s->minor < COMEDI_FIRST_SUBDEVICE_MINOR);
 
-	ret = kstrtouint(buf, 10, &new_size_kb);
-	if (ret)
-		return ret;
-	if (new_size_kb > (UINT_MAX / bytes_per_kibi))
-		return -EINVAL;
-	new_size = ((uint64_t) new_size_kb) * bytes_per_kibi;
+	spin_lock(&comedi_file_info_table_lock);
+	info = comedi_file_info_table[s->minor];
+	comedi_file_info_table[s->minor] = NULL;
+	spin_unlock(&comedi_file_info_table_lock);
 
-	mutex_lock(&info->device->mutex);
-	if (write_subdevice == NULL ||
-	    (write_subdevice->subdev_flags & SDF_CMD_WRITE) == 0 ||
-	    write_subdevice->async == NULL) {
-		mutex_unlock(&info->device->mutex);
-		return -EINVAL;
+	if (s->class_dev) {
+		device_destroy(comedi_class, MKDEV(COMEDI_MAJOR, s->minor));
+		s->class_dev = NULL;
 	}
-	retval = resize_async_buffer(info->device, write_subdevice,
-				     write_subdevice->async, new_size);
-	mutex_unlock(&info->device->mutex);
-
-	if (retval < 0)
-		return retval;
-	return count;
+	kfree(info);
 }
 
-static struct device_attribute dev_attr_write_buffer_kb = {
-	.attr = {
-		 .name = "write_buffer_kb",
-		 .mode = S_IRUGO | S_IWUSR | S_IWGRP},
-	.show = &show_write_buffer_kb,
-	.store = &store_write_buffer_kb
-};
+struct comedi_device_file_info *comedi_get_device_file_info(unsigned minor)
+{
+	struct comedi_device_file_info *info;
+
+	BUG_ON(minor >= COMEDI_NUM_MINORS);
+	spin_lock(&comedi_file_info_table_lock);
+	info = comedi_file_info_table[minor];
+	spin_unlock(&comedi_file_info_table_lock);
+	return info;
+}
+EXPORT_SYMBOL_GPL(comedi_get_device_file_info);