printer_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
{
	struct printer_dev		*dev = fd->private_data;
	unsigned long			flags;
	size_t				size;
	size_t				bytes_copied;
	struct usb_request		*req;
	/* This is a pointer to the current USB rx request. */
	struct usb_request		*current_rx_req;
	/* This is the number of bytes in the current rx buffer. */
	size_t				current_rx_bytes;
	/* This is a pointer to the current rx buffer. */
	u8				*current_rx_buf;

	if (len == 0)
		return -EINVAL;

	DBG(dev, "printer_read trying to read %d bytes\n", (int)len);

	mutex_lock(&dev->lock_printer_io);
	spin_lock_irqsave(&dev->lock, flags);

	if (dev->interface < 0) {
		spin_unlock_irqrestore(&dev->lock, flags);
		mutex_unlock(&dev->lock_printer_io);
		return -ENODEV;
	}

	/* We will use this flag later to check if a printer reset happened
	 * after we turn interrupts back on.
	 */
	dev->reset_printer = 0;

	setup_rx_reqs(dev);

	bytes_copied = 0;
	current_rx_req = dev->current_rx_req;
	current_rx_bytes = dev->current_rx_bytes;
	current_rx_buf = dev->current_rx_buf;
	dev->current_rx_req = NULL;
	dev->current_rx_bytes = 0;
	dev->current_rx_buf = NULL;

	/* Check if there is any data in the read buffers. Please note that
	 * current_rx_bytes is the number of bytes in the current rx buffer.
	 * If it is zero then check if there are any other rx_buffers that
	 * are on the completed list. We are only out of data if all rx
	 * buffers are empty.
	 */
	if ((current_rx_bytes == 0) &&
			(likely(list_empty(&dev->rx_buffers)))) {
		/* Turn interrupts back on before sleeping. */
		spin_unlock_irqrestore(&dev->lock, flags);

		/*
		 * If no data is available check if this is a NON-Blocking
		 * call or not.
		 */
		if (fd->f_flags & (O_NONBLOCK|O_NDELAY)) {
			mutex_unlock(&dev->lock_printer_io);
			return -EAGAIN;
		}

		/* Sleep until data is available */
		wait_event_interruptible(dev->rx_wait,
				(likely(!list_empty(&dev->rx_buffers))));
		spin_lock_irqsave(&dev->lock, flags);
	}

	/* We have data to return then copy it to the caller's buffer.*/
	while ((current_rx_bytes || likely(!list_empty(&dev->rx_buffers)))
			&& len) {
		if (current_rx_bytes == 0) {
			req = container_of(dev->rx_buffers.next,
					struct usb_request, list);
			list_del_init(&req->list);

			if (req->actual && req->buf) {
				current_rx_req = req;
				current_rx_bytes = req->actual;
				current_rx_buf = req->buf;
			} else {
				list_add(&req->list, &dev->rx_reqs);
				continue;
			}
		}

		/* Don't leave irqs off while doing memory copies */
		spin_unlock_irqrestore(&dev->lock, flags);

		if (len > current_rx_bytes)
			size = current_rx_bytes;
		else
			size = len;

		size -= copy_to_user(buf, current_rx_buf, size);
		bytes_copied += size;
		len -= size;
		buf += size;

		spin_lock_irqsave(&dev->lock, flags);

		/* We've disconnected or reset so return. */
		if (dev->reset_printer) {
			list_add(&current_rx_req->list, &dev->rx_reqs);
			spin_unlock_irqrestore(&dev->lock, flags);
			mutex_unlock(&dev->lock_printer_io);
			return -EAGAIN;
		}

		/* If we not returning all the data left in this RX request
		 * buffer then adjust the amount of data left in the buffer.
		 * Othewise if we are done with this RX request buffer then
		 * requeue it to get any incoming data from the USB host.
		 */
		if (size < current_rx_bytes) {
			current_rx_bytes -= size;
			current_rx_buf += size;
		} else {
			list_add(&current_rx_req->list, &dev->rx_reqs);
			current_rx_bytes = 0;
			current_rx_buf = NULL;
			current_rx_req = NULL;
		}
	}

	dev->current_rx_req = current_rx_req;
	dev->current_rx_bytes = current_rx_bytes;
	dev->current_rx_buf = current_rx_buf;

	spin_unlock_irqrestore(&dev->lock, flags);
	mutex_unlock(&dev->lock_printer_io);

	DBG(dev, "printer_read returned %d bytes\n", (int)bytes_copied);

	if (bytes_copied)
		return bytes_copied;
	else
		return -EAGAIN;
}
printer_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
{
	struct printer_dev		*dev = fd->private_data;
	unsigned long			flags;
	size_t				size;
	size_t				bytes_copied;
	struct usb_request		*req;
	 
	struct usb_request		*current_rx_req;
	 
	size_t				current_rx_bytes;
	 
	u8				*current_rx_buf;

	if (len == 0)
		return -EINVAL;

	DBG(dev, "printer_read trying to read %d bytes\n", (int)len);

	mutex_lock(&dev->lock_printer_io);
	spin_lock_irqsave(&dev->lock, flags);

	if (dev->interface < 0) {
		spin_unlock_irqrestore(&dev->lock, flags);
		mutex_unlock(&dev->lock_printer_io);
		return -ENODEV;
	}

	 
	dev->reset_printer = 0;

	setup_rx_reqs(dev);

	bytes_copied = 0;
	current_rx_req = dev->current_rx_req;
	current_rx_bytes = dev->current_rx_bytes;
	current_rx_buf = dev->current_rx_buf;
	dev->current_rx_req = NULL;
	dev->current_rx_bytes = 0;
	dev->current_rx_buf = NULL;

	 
	if ((current_rx_bytes == 0) &&
			(likely(list_empty(&dev->rx_buffers)))) {
		 
		spin_unlock_irqrestore(&dev->lock, flags);

		 
		if (fd->f_flags & (O_NONBLOCK|O_NDELAY)) {
			mutex_unlock(&dev->lock_printer_io);
			return -EAGAIN;
		}

		 
		wait_event_interruptible(dev->rx_wait,
				(likely(!list_empty(&dev->rx_buffers))));
		spin_lock_irqsave(&dev->lock, flags);
	}

	 
	while ((current_rx_bytes || likely(!list_empty(&dev->rx_buffers)))
			&& len) {
		if (current_rx_bytes == 0) {
			req = container_of(dev->rx_buffers.next,
					struct usb_request, list);
			list_del_init(&req->list);

			if (req->actual && req->buf) {
				current_rx_req = req;
				current_rx_bytes = req->actual;
				current_rx_buf = req->buf;
			} else {
				list_add(&req->list, &dev->rx_reqs);
				continue;
			}
		}

		 
		spin_unlock_irqrestore(&dev->lock, flags);

		if (len > current_rx_bytes)
			size = current_rx_bytes;
		else
			size = len;

		size -= copy_to_user(buf, current_rx_buf, size);
		bytes_copied += size;
		len -= size;
		buf += size;

		spin_lock_irqsave(&dev->lock, flags);

		 
		if (dev->reset_printer) {
			list_add(&current_rx_req->list, &dev->rx_reqs);
			spin_unlock_irqrestore(&dev->lock, flags);
			mutex_unlock(&dev->lock_printer_io);
			return -EAGAIN;
		}

		 
		if (size < current_rx_bytes) {
			current_rx_bytes -= size;
			current_rx_buf += size;
		} else {
			list_add(&current_rx_req->list, &dev->rx_reqs);
			current_rx_bytes = 0;
			current_rx_buf = NULL;
			current_rx_req = NULL;
		}
	}

	dev->current_rx_req = current_rx_req;
	dev->current_rx_bytes = current_rx_bytes;
	dev->current_rx_buf = current_rx_buf;

	spin_unlock_irqrestore(&dev->lock, flags);
	mutex_unlock(&dev->lock_printer_io);

	DBG(dev, "printer_read returned %d bytes\n", (int)bytes_copied);

	if (bytes_copied)
		return bytes_copied;
	else
		return -EAGAIN;
}