Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1088 insertions, 0 deletions

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
new file mode 100644
index 000000000000..dd4580cb57e0
--- /dev/null
+++ b/drivers/usb/misc/legousbtower.c
@@ -0,0 +1,1088 @@
+/*
+ * LEGO USB Tower driver
+ *
+ * Copyright (C) 2003 David Glance <davidgsf@sourceforge.net>
+ *               2001-2004 Juergen Stuber <starblue@users.sourceforge.net>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License as
+ *	published by the Free Software Foundation; either version 2 of
+ *	the License, or (at your option) any later version.
+ *
+ * derived from USB Skeleton driver - 0.5
+ * Copyright (C) 2001 Greg Kroah-Hartman (greg@kroah.com)
+ *
+ * History:
+ *
+ * 2001-10-13 - 0.1 js
+ *   - first version
+ * 2001-11-03 - 0.2 js
+ *   - simplified buffering, one-shot URBs for writing
+ * 2001-11-10 - 0.3 js
+ *   - removed IOCTL (setting power/mode is more complicated, postponed)
+ * 2001-11-28 - 0.4 js
+ *   - added vendor commands for mode of operation and power level in open
+ * 2001-12-04 - 0.5 js
+ *   - set IR mode by default (by oversight 0.4 set VLL mode)
+ * 2002-01-11 - 0.5? pcchan
+ *   - make read buffer reusable and work around bytes_to_write issue between
+ *     uhci and legusbtower
+ * 2002-09-23 - 0.52 david (david@csse.uwa.edu.au)
+ *   - imported into lejos project
+ *   - changed wake_up to wake_up_interruptible
+ *   - changed to use lego0 rather than tower0
+ *   - changed dbg() to use __func__ rather than deprecated __FUNCTION__
+ * 2003-01-12 - 0.53 david (david@csse.uwa.edu.au)
+ *   - changed read and write to write everything or
+ *     timeout (from a patch by Chris Riesen and Brett Thaeler driver)
+ *   - added ioctl functionality to set timeouts
+ * 2003-07-18 - 0.54 davidgsf (david@csse.uwa.edu.au)
+ *   - initial import into LegoUSB project
+ *   - merge of existing LegoUSB.c driver
+ * 2003-07-18 - 0.56 davidgsf (david@csse.uwa.edu.au)
+ *   - port to 2.6 style driver
+ * 2004-02-29 - 0.6 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - fix locking
+ *   - unlink read URBs which are no longer needed
+ *   - allow increased buffer size, eliminates need for timeout on write
+ *   - have read URB running continuously
+ *   - added poll
+ *   - forbid seeking
+ *   - added nonblocking I/O
+ *   - changed back __func__ to __FUNCTION__
+ *   - read and log tower firmware version
+ *   - reset tower on probe, avoids failure of first write
+ * 2004-03-09 - 0.7 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - timeout read now only after inactivity, shorten default accordingly
+ * 2004-03-11 - 0.8 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - log major, minor instead of possibly confusing device filename
+ *   - whitespace cleanup
+ * 2004-03-12 - 0.9 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - normalize whitespace in debug messages
+ *   - take care about endianness in control message responses
+ * 2004-03-13 - 0.91 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - make default intervals longer to accommodate current EHCI driver
+ * 2004-03-19 - 0.92 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - replaced atomic_t by memory barriers
+ * 2004-04-21 - 0.93 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - wait for completion of write urb in release (needed for remotecontrol)
+ *   - corrected poll for write direction (missing negation)
+ * 2004-04-22 - 0.94 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - make device locking interruptible
+ * 2004-04-30 - 0.95 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - check for valid udev on resubmitting and unlinking urbs
+ * 2004-08-03 - 0.96 Juergen Stuber <starblue@users.sourceforge.net>
+ *   - move reset into open to clean out spurious data
+ */
+
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/smp_lock.h>
+#include <linux/completion.h>
+#include <asm/uaccess.h>
+#include <linux/usb.h>
+#include <linux/poll.h>
+
+
+#ifdef CONFIG_USB_DEBUG
+	static int debug = 4;
+#else
+	static int debug = 0;
+#endif
+
+/* Use our own dbg macro */
+#undef dbg
+#define dbg(lvl, format, arg...) do { if (debug >= lvl) printk(KERN_DEBUG  __FILE__ ": " format "\n", ## arg); } while (0)
+
+
+/* Version Information */
+#define DRIVER_VERSION "v0.96"
+#define DRIVER_AUTHOR "Juergen Stuber <starblue@sourceforge.net>"
+#define DRIVER_DESC "LEGO USB Tower Driver"
+
+/* Module parameters */
+module_param(debug, int, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(debug, "Debug enabled or not");
+
+/* The defaults are chosen to work with the latest versions of leJOS and NQC.
+ */
+
+/* Some legacy software likes to receive packets in one piece.
+ * In this case read_buffer_size should exceed the maximal packet length
+ * (417 for datalog uploads), and packet_timeout should be set.
+ */
+static int read_buffer_size = 480;
+module_param(read_buffer_size, int, 0);
+MODULE_PARM_DESC(read_buffer_size, "Read buffer size");
+
+/* Some legacy software likes to send packets in one piece.
+ * In this case write_buffer_size should exceed the maximal packet length
+ * (417 for firmware and program downloads).
+ * A problem with long writes is that the following read may time out
+ * if the software is not prepared to wait long enough.
+ */
+static int write_buffer_size = 480;
+module_param(write_buffer_size, int, 0);
+MODULE_PARM_DESC(write_buffer_size, "Write buffer size");
+
+/* Some legacy software expects reads to contain whole LASM packets.
+ * To achieve this, characters which arrive before a packet timeout
+ * occurs will be returned in a single read operation.
+ * A problem with long reads is that the software may time out
+ * if it is not prepared to wait long enough.
+ * The packet timeout should be greater than the time between the
+ * reception of subsequent characters, which should arrive about
+ * every 5ms for the standard 2400 baud.
+ * Set it to 0 to disable.
+ */
+static int packet_timeout = 50;
+module_param(packet_timeout, int, 0);
+MODULE_PARM_DESC(packet_timeout, "Packet timeout in ms");
+
+/* Some legacy software expects blocking reads to time out.
+ * Timeout occurs after the specified time of read and write inactivity.
+ * Set it to 0 to disable.
+ */
+static int read_timeout = 200;
+module_param(read_timeout, int, 0);
+MODULE_PARM_DESC(read_timeout, "Read timeout in ms");
+
+/* As of kernel version 2.6.4 ehci-hcd uses an
+ * "only one interrupt transfer per frame" shortcut
+ * to simplify the scheduling of periodic transfers.
+ * This conflicts with our standard 1ms intervals for in and out URBs.
+ * We use default intervals of 2ms for in and 8ms for out transfers,
+ * which is fast enough for 2400 baud and allows a small additional load.
+ * Increase the interval to allow more devices that do interrupt transfers,
+ * or set to 0 to use the standard interval from the endpoint descriptors.
+ */
+static int interrupt_in_interval = 2;
+module_param(interrupt_in_interval, int, 0);
+MODULE_PARM_DESC(interrupt_in_interval, "Interrupt in interval in ms");
+
+static int interrupt_out_interval = 8;
+module_param(interrupt_out_interval, int, 0);
+MODULE_PARM_DESC(interrupt_out_interval, "Interrupt out interval in ms");
+
+/* Define these values to match your device */
+#define LEGO_USB_TOWER_VENDOR_ID	0x0694
+#define LEGO_USB_TOWER_PRODUCT_ID	0x0001
+
+/* Vendor requests */
+#define LEGO_USB_TOWER_REQUEST_RESET		0x04
+#define LEGO_USB_TOWER_REQUEST_GET_VERSION	0xFD
+
+struct tower_reset_reply {
+	__le16 size;		/* little-endian */
+	__u8 err_code;
+	__u8 spare;
+} __attribute__ ((packed));
+
+struct tower_get_version_reply {
+	__le16 size;		/* little-endian */
+	__u8 err_code;
+	__u8 spare;
+	__u8 major;
+	__u8 minor;
+	__le16 build_no;		/* little-endian */
+} __attribute__ ((packed));
+
+
+/* table of devices that work with this driver */
+static struct usb_device_id tower_table [] = {
+	{ USB_DEVICE(LEGO_USB_TOWER_VENDOR_ID, LEGO_USB_TOWER_PRODUCT_ID) },
+	{ }					/* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE (usb, tower_table);
+
+#define LEGO_USB_TOWER_MINOR_BASE	160
+
+
+/* Structure to hold all of our device specific stuff */
+struct lego_usb_tower {
+	struct semaphore	sem;		/* locks this structure */
+	struct usb_device*	udev;		/* save off the usb device pointer */
+	unsigned char		minor;		/* the starting minor number for this device */
+
+	int			open_count;	/* number of times this port has been opened */
+
+	char*			read_buffer;
+	size_t			read_buffer_length; /* this much came in */
+	size_t			read_packet_length; /* this much will be returned on read */
+	spinlock_t		read_buffer_lock;
+	int			packet_timeout_jiffies;
+	unsigned long		read_last_arrival;
+
+	wait_queue_head_t	read_wait;
+	wait_queue_head_t	write_wait;
+
+	char*			interrupt_in_buffer;
+	struct usb_endpoint_descriptor* interrupt_in_endpoint;
+	struct urb*		interrupt_in_urb;
+	int			interrupt_in_interval;
+	int			interrupt_in_running;
+	int			interrupt_in_done;
+
+	char*			interrupt_out_buffer;
+	struct usb_endpoint_descriptor* interrupt_out_endpoint;
+	struct urb*		interrupt_out_urb;
+	int			interrupt_out_interval;
+	int			interrupt_out_busy;
+
+};
+
+
+/* local function prototypes */
+static ssize_t tower_read	(struct file *file, char __user *buffer, size_t count, loff_t *ppos);
+static ssize_t tower_write	(struct file *file, const char __user *buffer, size_t count, loff_t *ppos);
+static inline void tower_delete (struct lego_usb_tower *dev);
+static int tower_open		(struct inode *inode, struct file *file);
+static int tower_release	(struct inode *inode, struct file *file);
+static unsigned int tower_poll	(struct file *file, poll_table *wait);
+static loff_t tower_llseek	(struct file *file, loff_t off, int whence);
+
+static void tower_abort_transfers (struct lego_usb_tower *dev);
+static void tower_check_for_read_packet (struct lego_usb_tower *dev);
+static void tower_interrupt_in_callback (struct urb *urb, struct pt_regs *regs);
+static void tower_interrupt_out_callback (struct urb *urb, struct pt_regs *regs);
+
+static int  tower_probe	(struct usb_interface *interface, const struct usb_device_id *id);
+static void tower_disconnect	(struct usb_interface *interface);
+
+
+/* prevent races between open() and disconnect */
+static DECLARE_MUTEX (disconnect_sem);
+
+/* file operations needed when we register this driver */
+static struct file_operations tower_fops = {
+	.owner =	THIS_MODULE,
+	.read  =	tower_read,
+	.write =	tower_write,
+	.open =		tower_open,
+	.release =	tower_release,
+	.poll =		tower_poll,
+	.llseek =	tower_llseek,
+};
+
+/*
+ * usb class driver info in order to get a minor number from the usb core,
+ * and to have the device registered with devfs and the driver core
+ */
+static struct usb_class_driver tower_class = {
+	.name =		"usb/legousbtower%d",
+	.fops =		&tower_fops,
+	.mode =		S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH,
+	.minor_base =	LEGO_USB_TOWER_MINOR_BASE,
+};
+
+
+/* usb specific object needed to register this driver with the usb subsystem */
+static struct usb_driver tower_driver = {
+	.owner =	THIS_MODULE,
+	.name =		"legousbtower",
+	.probe =	tower_probe,
+	.disconnect =	tower_disconnect,
+	.id_table =	tower_table,
+};
+
+
+/**
+ *	lego_usb_tower_debug_data
+ */
+static inline void lego_usb_tower_debug_data (int level, const char *function, int size, const unsigned char *data)
+{
+	int i;
+
+	if (debug < level)
+		return;
+
+	printk (KERN_DEBUG __FILE__": %s - length = %d, data = ", function, size);
+	for (i = 0; i < size; ++i) {
+		printk ("%.2x ", data[i]);
+	}
+	printk ("\n");
+}
+
+
+/**
+ *	tower_delete
+ */
+static inline void tower_delete (struct lego_usb_tower *dev)
+{
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	tower_abort_transfers (dev);
+
+	/* free data structures */
+	if (dev->interrupt_in_urb != NULL) {
+		usb_free_urb (dev->interrupt_in_urb);
+	}
+	if (dev->interrupt_out_urb != NULL) {
+		usb_free_urb (dev->interrupt_out_urb);
+	}
+	kfree (dev->read_buffer);
+	kfree (dev->interrupt_in_buffer);
+	kfree (dev->interrupt_out_buffer);
+	kfree (dev);
+
+	dbg(2, "%s: leave", __FUNCTION__);
+}
+
+
+/**
+ *	tower_open
+ */
+static int tower_open (struct inode *inode, struct file *file)
+{
+	struct lego_usb_tower *dev = NULL;
+	int subminor;
+	int retval = 0;
+	struct usb_interface *interface;
+	struct tower_reset_reply reset_reply;
+	int result;
+
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	nonseekable_open(inode, file);
+	subminor = iminor(inode);
+
+	down (&disconnect_sem);
+
+	interface = usb_find_interface (&tower_driver, subminor);
+
+	if (!interface) {
+		err ("%s - error, can't find device for minor %d",
+		     __FUNCTION__, subminor);
+		retval = -ENODEV;
+		goto unlock_disconnect_exit;
+	}
+
+	dev = usb_get_intfdata(interface);
+
+	if (!dev) {
+		retval = -ENODEV;
+		goto unlock_disconnect_exit;
+	}
+
+	/* lock this device */
+	if (down_interruptible (&dev->sem)) {
+	        retval = -ERESTARTSYS;
+		goto unlock_disconnect_exit;
+	}
+
+	/* allow opening only once */
+	if (dev->open_count) {
+		retval = -EBUSY;
+		goto unlock_exit;
+	}
+	dev->open_count = 1;
+
+	/* reset the tower */
+	result = usb_control_msg (dev->udev,
+				  usb_rcvctrlpipe(dev->udev, 0),
+				  LEGO_USB_TOWER_REQUEST_RESET,
+				  USB_TYPE_VENDOR | USB_DIR_IN | USB_RECIP_DEVICE,
+				  0,
+				  0,
+				  &reset_reply,
+				  sizeof(reset_reply),
+				  1000);
+	if (result < 0) {
+		err("LEGO USB Tower reset control request failed");
+		retval = result;
+		goto unlock_exit;
+	}
+
+	/* initialize in direction */
+	dev->read_buffer_length = 0;
+	dev->read_packet_length = 0;
+	usb_fill_int_urb (dev->interrupt_in_urb,
+			  dev->udev,
+			  usb_rcvintpipe(dev->udev, dev->interrupt_in_endpoint->bEndpointAddress),
+			  dev->interrupt_in_buffer,
+			  le16_to_cpu(dev->interrupt_in_endpoint->wMaxPacketSize),
+			  tower_interrupt_in_callback,
+			  dev,
+			  dev->interrupt_in_interval);
+
+	dev->interrupt_in_running = 1;
+	dev->interrupt_in_done = 0;
+	mb();
+
+	retval = usb_submit_urb (dev->interrupt_in_urb, GFP_KERNEL);
+	if (retval) {
+		err("Couldn't submit interrupt_in_urb %d", retval);
+		dev->interrupt_in_running = 0;
+		dev->open_count = 0;
+		goto unlock_exit;
+	}
+
+	/* save device in the file's private structure */
+	file->private_data = dev;
+
+unlock_exit:
+	up (&dev->sem);
+
+unlock_disconnect_exit:
+	up (&disconnect_sem);
+
+	dbg(2, "%s: leave, return value %d ", __FUNCTION__, retval);
+
+	return retval;
+}
+
+/**
+ *	tower_release
+ */
+static int tower_release (struct inode *inode, struct file *file)
+{
+	struct lego_usb_tower *dev;
+	int retval = 0;
+
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	dev = (struct lego_usb_tower *)file->private_data;
+
+	if (dev == NULL) {
+		dbg(1, "%s: object is NULL", __FUNCTION__);
+		retval = -ENODEV;
+		goto exit;
+	}
+
+	if (down_interruptible (&dev->sem)) {
+	        retval = -ERESTARTSYS;
+		goto exit;
+	}
+
+	if (dev->open_count != 1) {
+		dbg(1, "%s: device not opened exactly once", __FUNCTION__);
+		retval = -ENODEV;
+		goto unlock_exit;
+	}
+	if (dev->udev == NULL) {
+		/* the device was unplugged before the file was released */
+		up (&dev->sem);	/* unlock here as tower_delete frees dev */
+		tower_delete (dev);
+		goto exit;
+	}
+
+	/* wait until write transfer is finished */
+	if (dev->interrupt_out_busy) {
+		wait_event_interruptible_timeout (dev->write_wait, !dev->interrupt_out_busy, 2 * HZ);
+	}
+	tower_abort_transfers (dev);
+	dev->open_count = 0;
+
+unlock_exit:
+	up (&dev->sem);
+
+exit:
+	dbg(2, "%s: leave, return value %d", __FUNCTION__, retval);
+	return retval;
+}
+
+
+/**
+ *	tower_abort_transfers
+ *      aborts transfers and frees associated data structures
+ */
+static void tower_abort_transfers (struct lego_usb_tower *dev)
+{
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	if (dev == NULL) {
+		dbg(1, "%s: dev is null", __FUNCTION__);
+		goto exit;
+	}
+
+	/* shutdown transfer */
+	if (dev->interrupt_in_running) {
+		dev->interrupt_in_running = 0;
+		mb();
+		if (dev->interrupt_in_urb != NULL && dev->udev) {
+			usb_kill_urb (dev->interrupt_in_urb);
+		}
+	}
+	if (dev->interrupt_out_busy) {
+		if (dev->interrupt_out_urb != NULL && dev->udev) {
+			usb_kill_urb (dev->interrupt_out_urb);
+		}
+	}
+
+exit:
+	dbg(2, "%s: leave", __FUNCTION__);
+}
+
+
+/**
+ *	tower_check_for_read_packet
+ *
+ *      To get correct semantics for signals and non-blocking I/O
+ *      with packetizing we pretend not to see any data in the read buffer
+ *      until it has been there unchanged for at least
+ *      dev->packet_timeout_jiffies, or until the buffer is full.
+ */
+static void tower_check_for_read_packet (struct lego_usb_tower *dev)
+{
+	spin_lock_irq (&dev->read_buffer_lock);
+	if (!packet_timeout
+	    || time_after(jiffies, dev->read_last_arrival + dev->packet_timeout_jiffies)
+	    || dev->read_buffer_length == read_buffer_size) {
+		dev->read_packet_length = dev->read_buffer_length;
+	}
+	dev->interrupt_in_done = 0;
+	spin_unlock_irq (&dev->read_buffer_lock);
+}
+
+
+/**
+ *	tower_poll
+ */
+static unsigned int tower_poll (struct file *file, poll_table *wait)
+{
+	struct lego_usb_tower *dev;
+	unsigned int mask = 0;
+
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	dev = file->private_data;
+
+	poll_wait(file, &dev->read_wait, wait);
+	poll_wait(file, &dev->write_wait, wait);
+
+	tower_check_for_read_packet(dev);
+	if (dev->read_packet_length > 0) {
+		mask |= POLLIN | POLLRDNORM;
+	}
+	if (!dev->interrupt_out_busy) {
+		mask |= POLLOUT | POLLWRNORM;
+	}
+
+	dbg(2, "%s: leave, mask = %d", __FUNCTION__, mask);
+
+	return mask;
+}
+
+
+/**
+ *	tower_llseek
+ */
+static loff_t tower_llseek (struct file *file, loff_t off, int whence)
+{
+	return -ESPIPE;		/* unseekable */
+}
+
+
+/**
+ *	tower_read
+ */
+static ssize_t tower_read (struct file *file, char __user *buffer, size_t count, loff_t *ppos)
+{
+	struct lego_usb_tower *dev;
+	size_t bytes_to_read;
+	int i;
+	int retval = 0;
+	unsigned long timeout = 0;
+
+	dbg(2, "%s: enter, count = %Zd", __FUNCTION__, count);
+
+	dev = (struct lego_usb_tower *)file->private_data;
+
+	/* lock this object */
+	if (down_interruptible (&dev->sem)) {
+		retval = -ERESTARTSYS;
+		goto exit;
+	}
+
+	/* verify that the device wasn't unplugged */
+	if (dev->udev == NULL) {
+		retval = -ENODEV;
+		err("No device or device unplugged %d", retval);
+		goto unlock_exit;
+	}
+
+	/* verify that we actually have some data to read */
+	if (count == 0) {
+		dbg(1, "%s: read request of 0 bytes", __FUNCTION__);
+		goto unlock_exit;
+	}
+
+	if (read_timeout) {
+		timeout = jiffies + read_timeout * HZ / 1000;
+	}
+
+	/* wait for data */
+	tower_check_for_read_packet (dev);
+	while (dev->read_packet_length == 0) {
+		if (file->f_flags & O_NONBLOCK) {
+			retval = -EAGAIN;
+			goto unlock_exit;
+		}
+		retval = wait_event_interruptible_timeout(dev->read_wait, dev->interrupt_in_done, dev->packet_timeout_jiffies);
+		if (retval < 0) {
+			goto unlock_exit;
+		}
+
+		/* reset read timeout during read or write activity */
+		if (read_timeout
+		    && (dev->read_buffer_length || dev->interrupt_out_busy)) {
+			timeout = jiffies + read_timeout * HZ / 1000;
+		}
+		/* check for read timeout */
+		if (read_timeout && time_after (jiffies, timeout)) {
+			retval = -ETIMEDOUT;
+			goto unlock_exit;
+		}
+		tower_check_for_read_packet (dev);
+	}
+
+	/* copy the data from read_buffer into userspace */
+	bytes_to_read = min(count, dev->read_packet_length);
+
+	if (copy_to_user (buffer, dev->read_buffer, bytes_to_read)) {
+		retval = -EFAULT;
+		goto unlock_exit;
+	}
+
+	spin_lock_irq (&dev->read_buffer_lock);
+	dev->read_buffer_length -= bytes_to_read;
+	dev->read_packet_length -= bytes_to_read;
+	for (i=0; i<dev->read_buffer_length; i++) {
+		dev->read_buffer[i] = dev->read_buffer[i+bytes_to_read];
+	}
+	spin_unlock_irq (&dev->read_buffer_lock);
+
+	retval = bytes_to_read;
+
+unlock_exit:
+	/* unlock the device */
+	up (&dev->sem);
+
+exit:
+	dbg(2, "%s: leave, return value %d", __FUNCTION__, retval);
+	return retval;
+}
+
+
+/**
+ *	tower_write
+ */
+static ssize_t tower_write (struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
+{
+	struct lego_usb_tower *dev;
+	size_t bytes_to_write;
+	int retval = 0;
+
+	dbg(2, "%s: enter, count = %Zd", __FUNCTION__, count);
+
+	dev = (struct lego_usb_tower *)file->private_data;
+
+	/* lock this object */
+	if (down_interruptible (&dev->sem)) {
+		retval = -ERESTARTSYS;
+		goto exit;
+	}
+
+	/* verify that the device wasn't unplugged */
+	if (dev->udev == NULL) {
+		retval = -ENODEV;
+		err("No device or device unplugged %d", retval);
+		goto unlock_exit;
+	}
+
+	/* verify that we actually have some data to write */
+	if (count == 0) {
+		dbg(1, "%s: write request of 0 bytes", __FUNCTION__);
+		goto unlock_exit;
+	}
+
+	/* wait until previous transfer is finished */
+	while (dev->interrupt_out_busy) {
+		if (file->f_flags & O_NONBLOCK) {
+			retval = -EAGAIN;
+			goto unlock_exit;
+		}
+		retval = wait_event_interruptible (dev->write_wait, !dev->interrupt_out_busy);
+		if (retval) {
+			goto unlock_exit;
+		}
+	}
+
+	/* write the data into interrupt_out_buffer from userspace */
+	bytes_to_write = min_t(int, count, write_buffer_size);
+	dbg(4, "%s: count = %Zd, bytes_to_write = %Zd", __FUNCTION__, count, bytes_to_write);
+
+	if (copy_from_user (dev->interrupt_out_buffer, buffer, bytes_to_write)) {
+		retval = -EFAULT;
+		goto unlock_exit;
+	}
+
+	/* send off the urb */
+	usb_fill_int_urb(dev->interrupt_out_urb,
+			 dev->udev,
+			 usb_sndintpipe(dev->udev, dev->interrupt_out_endpoint->bEndpointAddress),
+			 dev->interrupt_out_buffer,
+			 bytes_to_write,
+			 tower_interrupt_out_callback,
+			 dev,
+			 dev->interrupt_out_interval);
+
+	dev->interrupt_out_busy = 1;
+	wmb();
+
+	retval = usb_submit_urb (dev->interrupt_out_urb, GFP_KERNEL);
+	if (retval) {
+		dev->interrupt_out_busy = 0;
+		err("Couldn't submit interrupt_out_urb %d", retval);
+		goto unlock_exit;
+	}
+	retval = bytes_to_write;
+
+unlock_exit:
+	/* unlock the device */
+	up (&dev->sem);
+
+exit:
+	dbg(2, "%s: leave, return value %d", __FUNCTION__, retval);
+
+	return retval;
+}
+
+
+/**
+ *	tower_interrupt_in_callback
+ */
+static void tower_interrupt_in_callback (struct urb *urb, struct pt_regs *regs)
+{
+	struct lego_usb_tower *dev = (struct lego_usb_tower *)urb->context;
+	int retval;
+
+	dbg(4, "%s: enter, status %d", __FUNCTION__, urb->status);
+
+	lego_usb_tower_debug_data(5, __FUNCTION__, urb->actual_length, urb->transfer_buffer);
+
+	if (urb->status) {
+		if (urb->status == -ENOENT ||
+		    urb->status == -ECONNRESET ||
+		    urb->status == -ESHUTDOWN) {
+			goto exit;
+		} else {
+			dbg(1, "%s: nonzero status received: %d", __FUNCTION__, urb->status);
+			goto resubmit; /* maybe we can recover */
+		}
+	}
+
+	if (urb->actual_length > 0) {
+		spin_lock (&dev->read_buffer_lock);
+		if (dev->read_buffer_length + urb->actual_length < read_buffer_size) {
+			memcpy (dev->read_buffer + dev->read_buffer_length,
+				dev->interrupt_in_buffer,
+				urb->actual_length);
+			dev->read_buffer_length += urb->actual_length;
+			dev->read_last_arrival = jiffies;
+			dbg(3, "%s: received %d bytes", __FUNCTION__, urb->actual_length);
+		} else {
+			printk(KERN_WARNING "%s: read_buffer overflow, %d bytes dropped", __FUNCTION__, urb->actual_length);
+		}
+		spin_unlock (&dev->read_buffer_lock);
+	}
+
+resubmit:
+	/* resubmit if we're still running */
+	if (dev->interrupt_in_running && dev->udev) {
+		retval = usb_submit_urb (dev->interrupt_in_urb, GFP_ATOMIC);
+		if (retval) {
+			err("%s: usb_submit_urb failed (%d)", __FUNCTION__, retval);
+		}
+	}
+
+exit:
+	dev->interrupt_in_done = 1;
+	wake_up_interruptible (&dev->read_wait);
+
+	lego_usb_tower_debug_data(5, __FUNCTION__, urb->actual_length, urb->transfer_buffer);
+	dbg(4, "%s: leave, status %d", __FUNCTION__, urb->status);
+}
+
+
+/**
+ *	tower_interrupt_out_callback
+ */
+static void tower_interrupt_out_callback (struct urb *urb, struct pt_regs *regs)
+{
+	struct lego_usb_tower *dev = (struct lego_usb_tower *)urb->context;
+
+	dbg(4, "%s: enter, status %d", __FUNCTION__, urb->status);
+	lego_usb_tower_debug_data(5, __FUNCTION__, urb->actual_length, urb->transfer_buffer);
+
+	/* sync/async unlink faults aren't errors */
+	if (urb->status && !(urb->status == -ENOENT ||
+			     urb->status == -ECONNRESET ||
+			     urb->status == -ESHUTDOWN)) {
+		dbg(1, "%s - nonzero write bulk status received: %d",
+		    __FUNCTION__, urb->status);
+	}
+
+	dev->interrupt_out_busy = 0;
+	wake_up_interruptible(&dev->write_wait);
+
+	lego_usb_tower_debug_data(5, __FUNCTION__, urb->actual_length, urb->transfer_buffer);
+	dbg(4, "%s: leave, status %d", __FUNCTION__, urb->status);
+}
+
+
+/**
+ *	tower_probe
+ *
+ *	Called by the usb core when a new device is connected that it thinks
+ *	this driver might be interested in.
+ */
+static int tower_probe (struct usb_interface *interface, const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(interface);
+	struct lego_usb_tower *dev = NULL;
+	struct usb_host_interface *iface_desc;
+	struct usb_endpoint_descriptor* endpoint;
+	struct tower_get_version_reply get_version_reply;
+	int i;
+	int retval = -ENOMEM;
+	int result;
+
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	if (udev == NULL) {
+		info ("udev is NULL.");
+	}
+
+	/* allocate memory for our device state and intialize it */
+
+	dev = kmalloc (sizeof(struct lego_usb_tower), GFP_KERNEL);
+
+	if (dev == NULL) {
+		err ("Out of memory");
+		goto exit;
+	}
+
+	init_MUTEX (&dev->sem);
+
+	dev->udev = udev;
+	dev->open_count = 0;
+
+	dev->read_buffer = NULL;
+	dev->read_buffer_length = 0;
+	dev->read_packet_length = 0;
+	spin_lock_init (&dev->read_buffer_lock);
+	dev->packet_timeout_jiffies = packet_timeout * HZ / 1000;
+	dev->read_last_arrival = jiffies;
+
+	init_waitqueue_head (&dev->read_wait);
+	init_waitqueue_head (&dev->write_wait);
+
+	dev->interrupt_in_buffer = NULL;
+	dev->interrupt_in_endpoint = NULL;
+	dev->interrupt_in_urb = NULL;
+	dev->interrupt_in_running = 0;
+	dev->interrupt_in_done = 0;
+
+	dev->interrupt_out_buffer = NULL;
+	dev->interrupt_out_endpoint = NULL;
+	dev->interrupt_out_urb = NULL;
+	dev->interrupt_out_busy = 0;
+
+	iface_desc = interface->cur_altsetting;
+
+	/* set up the endpoint information */
+	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
+		endpoint = &iface_desc->endpoint[i].desc;
+
+		if (((endpoint->bEndpointAddress & USB_ENDPOINT_DIR_MASK) == USB_DIR_IN) &&
+		    ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) == USB_ENDPOINT_XFER_INT)) {
+			dev->interrupt_in_endpoint = endpoint;
+		}
+
+		if (((endpoint->bEndpointAddress & USB_ENDPOINT_DIR_MASK) == USB_DIR_OUT) &&
+		    ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) == USB_ENDPOINT_XFER_INT)) {
+			dev->interrupt_out_endpoint = endpoint;
+		}
+	}
+	if(dev->interrupt_in_endpoint == NULL) {
+		err("interrupt in endpoint not found");
+		goto error;
+	}
+	if (dev->interrupt_out_endpoint == NULL) {
+		err("interrupt out endpoint not found");
+		goto error;
+	}
+
+	dev->read_buffer = kmalloc (read_buffer_size, GFP_KERNEL);
+	if (!dev->read_buffer) {
+		err("Couldn't allocate read_buffer");
+		goto error;
+	}
+	dev->interrupt_in_buffer = kmalloc (le16_to_cpu(dev->interrupt_in_endpoint->wMaxPacketSize), GFP_KERNEL);
+	if (!dev->interrupt_in_buffer) {
+		err("Couldn't allocate interrupt_in_buffer");
+		goto error;
+	}
+	dev->interrupt_in_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!dev->interrupt_in_urb) {
+		err("Couldn't allocate interrupt_in_urb");
+		goto error;
+	}
+	dev->interrupt_out_buffer = kmalloc (write_buffer_size, GFP_KERNEL);
+	if (!dev->interrupt_out_buffer) {
+		err("Couldn't allocate interrupt_out_buffer");
+		goto error;
+	}
+	dev->interrupt_out_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!dev->interrupt_out_urb) {
+		err("Couldn't allocate interrupt_out_urb");
+		goto error;
+	}
+	dev->interrupt_in_interval = interrupt_in_interval ? interrupt_in_interval : dev->interrupt_in_endpoint->bInterval;
+	dev->interrupt_out_interval = interrupt_out_interval ? interrupt_out_interval : dev->interrupt_out_endpoint->bInterval;
+
+	/* we can register the device now, as it is ready */
+	usb_set_intfdata (interface, dev);
+
+	retval = usb_register_dev (interface, &tower_class);
+
+	if (retval) {
+		/* something prevented us from registering this driver */
+		err ("Not able to get a minor for this device.");
+		usb_set_intfdata (interface, NULL);
+		goto error;
+	}
+	dev->minor = interface->minor;
+
+	/* let the user know what node this device is now attached to */
+	info ("LEGO USB Tower #%d now attached to major %d minor %d", (dev->minor - LEGO_USB_TOWER_MINOR_BASE), USB_MAJOR, dev->minor);
+
+	/* get the firmware version and log it */
+	result = usb_control_msg (udev,
+				  usb_rcvctrlpipe(udev, 0),
+				  LEGO_USB_TOWER_REQUEST_GET_VERSION,
+				  USB_TYPE_VENDOR | USB_DIR_IN | USB_RECIP_DEVICE,
+				  0,
+				  0,
+				  &get_version_reply,
+				  sizeof(get_version_reply),
+				  1000);
+	if (result < 0) {
+		err("LEGO USB Tower get version control request failed");
+		retval = result;
+		goto error;
+	}
+	info("LEGO USB Tower firmware version is %d.%d build %d",
+	     get_version_reply.major,
+	     get_version_reply.minor,
+	     le16_to_cpu(get_version_reply.build_no));
+
+
+exit:
+	dbg(2, "%s: leave, return value 0x%.8lx (dev)", __FUNCTION__, (long) dev);
+
+	return retval;
+
+error:
+	tower_delete(dev);
+	return retval;
+}
+
+
+/**
+ *	tower_disconnect
+ *
+ *	Called by the usb core when the device is removed from the system.
+ */
+static void tower_disconnect (struct usb_interface *interface)
+{
+	struct lego_usb_tower *dev;
+	int minor;
+
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	down (&disconnect_sem);
+
+	dev = usb_get_intfdata (interface);
+	usb_set_intfdata (interface, NULL);
+
+
+	down (&dev->sem);
+
+	minor = dev->minor;
+
+	/* give back our minor */
+	usb_deregister_dev (interface, &tower_class);
+
+	/* if the device is not opened, then we clean up right now */
+	if (!dev->open_count) {
+		up (&dev->sem);
+		tower_delete (dev);
+	} else {
+		dev->udev = NULL;
+		up (&dev->sem);
+	}
+
+	up (&disconnect_sem);
+
+	info("LEGO USB Tower #%d now disconnected", (minor - LEGO_USB_TOWER_MINOR_BASE));
+
+	dbg(2, "%s: leave", __FUNCTION__);
+}
+
+
+
+/**
+ *	lego_usb_tower_init
+ */
+static int __init lego_usb_tower_init(void)
+{
+	int result;
+	int retval = 0;
+
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	/* register this driver with the USB subsystem */
+	result = usb_register(&tower_driver);
+	if (result < 0) {
+		err("usb_register failed for the "__FILE__" driver. Error number %d", result);
+		retval = -1;
+		goto exit;
+	}
+
+	info(DRIVER_DESC " " DRIVER_VERSION);
+
+exit:
+	dbg(2, "%s: leave, return value %d", __FUNCTION__, retval);
+
+	return retval;
+}
+
+
+/**
+ *	lego_usb_tower_exit
+ */
+static void __exit lego_usb_tower_exit(void)
+{
+	dbg(2, "%s: enter", __FUNCTION__);
+
+	/* deregister this driver with the USB subsystem */
+	usb_deregister (&tower_driver);
+
+	dbg(2, "%s: leave", __FUNCTION__);
+}
+
+module_init (lego_usb_tower_init);
+module_exit (lego_usb_tower_exit);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+#ifdef MODULE_LICENSE
+MODULE_LICENSE("GPL");
+#endif