[PATCH] USB: add ldusb driver

The following driver provides complete interrupt-in and interrupt-out
reports (raw data) to a user program. Until now it uses the
HIDIOCGDEVINFO ioctl call, because I don't know better :-(. Perhaps, it
will be ok for you - and I will be happy, if you assign 8 minor numbers.

I have tested it in several environments and it works very well for me.
However, it has a problem with two or more devices at the same hub, if
the two or more devices need 1 ms interrupt-in transfers. Unfortunately
more than one interrupt-in transfer every ms isn't possible (ehci
driver?). This is why the min_interrupt_in_interval and
min_interrupt_out_interval are increased to 2 ms (see the corresponding
module parameters). This way, I can use two devices simultaneously at
the same hub.

Signed-off-by: Michael Hund <mhund@ld-didactic.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 805 insertions, 0 deletions

diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
index 3a89695..6649531 100644
--- a/drivers/usb/misc/Kconfig
+++ b/drivers/usb/misc/Kconfig
@@ -139,6 +139,16 @@ config USB_IDMOUSE
 
 source "drivers/usb/misc/sisusbvga/Kconfig"
 
+config USB_LD
+	tristate "USB LD driver"
+	depends on USB && EXPERIMENTAL
+	help
+	  This driver is for generic USB devices that use interrupt transfers,
+	  like LD Didactic's USB devices.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ldusb.
+
 config USB_TEST
 	tristate "USB testing driver (DEVELOPMENT)"
 	depends on USB && USB_DEVICEFS && EXPERIMENTAL
diff --git a/drivers/usb/misc/Makefile b/drivers/usb/misc/Makefile
index 4a3814c..862e40a 100644
--- a/drivers/usb/misc/Makefile
+++ b/drivers/usb/misc/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_USB_EMI26)		+= emi26.o
 obj-$(CONFIG_USB_EMI62)		+= emi62.o
 obj-$(CONFIG_USB_IDMOUSE)	+= idmouse.o
 obj-$(CONFIG_USB_LCD)		+= usblcd.o
+obj-$(CONFIG_USB_LD)		+= ldusb.o
 obj-$(CONFIG_USB_LED)		+= usbled.o
 obj-$(CONFIG_USB_LEGOTOWER)	+= legousbtower.o
 obj-$(CONFIG_USB_PHIDGETKIT)	+= phidgetkit.o
diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
new file mode 100644
index 0000000..66ec883
--- /dev/null
+++ b/drivers/usb/misc/ldusb.c
@@ -0,0 +1,794 @@
+/**
+ * Generic USB driver for report based interrupt in/out devices
+ * like LD Didactic's USB devices. LD Didactic's USB devices are
+ * HID devices which do not use HID report definitons (they use
+ * raw interrupt in and our reports only for communication).
+ *
+ * This driver uses a ring buffer for time critical reading of
+ * interrupt in reports and provides read and write methods for
+ * raw interrupt reports (similar to the Windows HID driver).
+ * Devices based on the book USB COMPLETE by Jan Axelson may need
+ * such a compatibility to the Windows HID driver.
+ *
+ * Copyright (C) 2005 Michael Hund <mhund@ld-didactic.de>
+ *
+ *	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 Lego USB Tower driver
+ * Copyright (C) 2003 David Glance <advidgsf@sourceforge.net>
+ *		 2001-2004 Juergen Stuber <starblue@users.sourceforge.net>
+ *
+ * V0.1  (mh) Initial version
+ * V0.11 (mh) Added raw support for HID 1.0 devices (no interrupt out endpoint)
+ */
+
+#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 <asm/uaccess.h>
+#include <linux/input.h>
+#include <linux/usb.h>
+#include <linux/poll.h>
+
+/* Define these values to match your devices */
+#define USB_VENDOR_ID_LD		0x0f11	/* USB Vendor ID of LD Didactic GmbH */
+#define USB_DEVICE_ID_CASSY		0x1000	/* USB Product ID for all CASSY-S modules */
+#define USB_DEVICE_ID_POCKETCASSY	0x1010	/* USB Product ID for Pocket-CASSY */
+#define USB_DEVICE_ID_MOBILECASSY	0x1020	/* USB Product ID for Mobile-CASSY */
+#define USB_DEVICE_ID_JWM		0x1080	/* USB Product ID for Joule and Wattmeter */
+#define USB_DEVICE_ID_DMMP		0x1081	/* USB Product ID for Digital Multimeter P (reserved) */
+#define USB_DEVICE_ID_UMIP		0x1090	/* USB Product ID for UMI P */
+#define USB_DEVICE_ID_VIDEOCOM		0x1200	/* USB Product ID for VideoCom */
+#define USB_DEVICE_ID_COM3LAB		0x2000	/* USB Product ID for COM3LAB */
+#define USB_DEVICE_ID_TELEPORT		0x2010	/* USB Product ID for Terminal Adapter */
+#define USB_DEVICE_ID_NETWORKANALYSER	0x2020	/* USB Product ID for Network Analyser */
+#define USB_DEVICE_ID_POWERCONTROL	0x2030	/* USB Product ID for Controlling device for Power Electronics */
+
+#define USB_VENDOR_ID_VERNIER		0x08f7
+#define USB_DEVICE_ID_VERNIER_LABPRO	0x0001
+#define USB_DEVICE_ID_VERNIER_GOTEMP	0x0002
+#define USB_DEVICE_ID_VERNIER_SKIP	0x0003
+#define USB_DEVICE_ID_VERNIER_CYCLOPS	0x0004
+
+
+#ifdef CONFIG_USB_DYNAMIC_MINORS
+#define USB_LD_MINOR_BASE	0
+#else
+#define USB_LD_MINOR_BASE	176
+#endif
+
+/* table of devices that work with this driver */
+static struct usb_device_id ld_usb_table [] = {
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_CASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_POCKETCASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_MOBILECASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_JWM) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_DMMP) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_UMIP) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_VIDEOCOM) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_COM3LAB) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_TELEPORT) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_NETWORKANALYSER) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_POWERCONTROL) },
+	{ USB_DEVICE(USB_VENDOR_ID_VERNIER, USB_DEVICE_ID_VERNIER_LABPRO) },
+	{ USB_DEVICE(USB_VENDOR_ID_VERNIER, USB_DEVICE_ID_VERNIER_GOTEMP) },
+	{ USB_DEVICE(USB_VENDOR_ID_VERNIER, USB_DEVICE_ID_VERNIER_SKIP) },
+	{ USB_DEVICE(USB_VENDOR_ID_VERNIER, USB_DEVICE_ID_VERNIER_CYCLOPS) },
+	{ }					/* Terminating entry */
+};
+MODULE_DEVICE_TABLE(usb, ld_usb_table);
+MODULE_VERSION("V0.11");
+MODULE_AUTHOR("Michael Hund <mhund@ld-didactic.de>");
+MODULE_DESCRIPTION("LD USB Driver");
+MODULE_LICENSE("GPL");
+MODULE_SUPPORTED_DEVICE("LD USB Devices");
+
+#ifdef CONFIG_USB_DEBUG
+	static int debug = 1;
+#else
+	static int debug = 0;
+#endif
+
+/* Use our own dbg macro */
+#define dbg_info(dev, format, arg...) do { if (debug) dev_info(dev , format , ## arg); } while (0)
+
+/* Module parameters */
+module_param(debug, int, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(debug, "Debug enabled or not");
+
+/* All interrupt in transfers are collected in a ring buffer to
+ * avoid racing conditions and get better performance of the driver.
+ */
+static int ring_buffer_size = 128;
+module_param(ring_buffer_size, int, 0);
+MODULE_PARM_DESC(ring_buffer_size, "Read ring buffer size in reports");
+
+/* The write_buffer can contain more than one interrupt out transfer.
+ */
+static int write_buffer_size = 10;
+module_param(write_buffer_size, int, 0);
+MODULE_PARM_DESC(write_buffer_size, "Write buffer size in reports");
+
+/* 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 2ms for out transfers,
+ * which should be fast enough.
+ * Increase the interval to allow more devices that do interrupt transfers,
+ * or set to 1 to use the standard interval from the endpoint descriptors.
+ */
+static int min_interrupt_in_interval = 2;
+module_param(min_interrupt_in_interval, int, 0);
+MODULE_PARM_DESC(min_interrupt_in_interval, "Minimum interrupt in interval in ms");
+
+static int min_interrupt_out_interval = 2;
+module_param(min_interrupt_out_interval, int, 0);
+MODULE_PARM_DESC(min_interrupt_out_interval, "Minimum interrupt out interval in ms");
+
+/* Structure to hold all of our device specific stuff */
+struct ld_usb {
+	struct semaphore	sem;		/* locks this structure */
+	struct usb_interface*	intf;		/* save off the usb interface pointer */
+
+	int			open_count;	/* number of times this port has been opened */
+
+	char*			ring_buffer;
+	unsigned int		ring_head;
+	unsigned int		ring_tail;
+
+	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;
+	size_t			interrupt_in_endpoint_size;
+	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;
+	size_t			interrupt_out_endpoint_size;
+	int			interrupt_out_busy;
+};
+
+/* prevent races between open() and disconnect() */
+static DECLARE_MUTEX(disconnect_sem);
+
+static struct usb_driver ld_usb_driver;
+
+/**
+ *	ld_usb_abort_transfers
+ *      aborts transfers and frees associated data structures
+ */
+static void ld_usb_abort_transfers(struct ld_usb *dev)
+{
+	/* shutdown transfer */
+	if (dev->interrupt_in_running) {
+		dev->interrupt_in_running = 0;
+		if (dev->intf)
+			usb_kill_urb(dev->interrupt_in_urb);
+	}
+	if (dev->interrupt_out_busy)
+		if (dev->intf)
+			usb_kill_urb(dev->interrupt_out_urb);
+}
+
+/**
+ *	ld_usb_delete
+ */
+static void ld_usb_delete(struct ld_usb *dev)
+{
+	ld_usb_abort_transfers(dev);
+
+	/* free data structures */
+	usb_free_urb(dev->interrupt_in_urb);
+	usb_free_urb(dev->interrupt_out_urb);
+	kfree(dev->ring_buffer);
+	kfree(dev->interrupt_in_buffer);
+	kfree(dev->interrupt_out_buffer);
+	kfree(dev);
+}
+
+/**
+ *	ld_usb_interrupt_in_callback
+ */
+static void ld_usb_interrupt_in_callback(struct urb *urb, struct pt_regs *regs)
+{
+	struct ld_usb *dev = urb->context;
+	size_t *actual_buffer;
+	unsigned int next_ring_head;
+	int retval;
+
+	if (urb->status) {
+		if (urb->status == -ENOENT ||
+		    urb->status == -ECONNRESET ||
+		    urb->status == -ESHUTDOWN) {
+			goto exit;
+		} else {
+			dbg_info(&dev->intf->dev, "%s: nonzero status received: %d\n",
+				 __FUNCTION__, urb->status);
+			goto resubmit; /* maybe we can recover */
+		}
+	}
+
+	if (urb->actual_length > 0) {
+		next_ring_head = (dev->ring_head+1) % ring_buffer_size;
+		if (next_ring_head != dev->ring_tail) {
+			actual_buffer = (size_t*)(dev->ring_buffer + dev->ring_head*(sizeof(size_t)+dev->interrupt_in_endpoint_size));
+			/* actual_buffer gets urb->actual_length + interrupt_in_buffer */
+			*actual_buffer = urb->actual_length;
+			memcpy(actual_buffer+1, dev->interrupt_in_buffer, urb->actual_length);
+			dev->ring_head = next_ring_head;
+			dbg_info(&dev->intf->dev, "%s: received %d bytes\n",
+				 __FUNCTION__, urb->actual_length);
+		} else
+			dev_warn(&dev->intf->dev,
+				 "Ring buffer overflow, %d bytes dropped\n",
+				 urb->actual_length);
+	}
+
+resubmit:
+	/* resubmit if we're still running */
+	if (dev->interrupt_in_running && dev->intf) {
+		retval = usb_submit_urb(dev->interrupt_in_urb, GFP_ATOMIC);
+		if (retval)
+			dev_err(&dev->intf->dev,
+				"usb_submit_urb failed (%d)\n", retval);
+	}
+
+exit:
+	dev->interrupt_in_done = 1;
+	wake_up_interruptible(&dev->read_wait);
+}
+
+/**
+ *	ld_usb_interrupt_out_callback
+ */
+static void ld_usb_interrupt_out_callback(struct urb *urb, struct pt_regs *regs)
+{
+	struct ld_usb *dev = urb->context;
+
+	/* sync/async unlink faults aren't errors */
+	if (urb->status && !(urb->status == -ENOENT ||
+			     urb->status == -ECONNRESET ||
+			     urb->status == -ESHUTDOWN))
+		dbg_info(&dev->intf->dev,
+			 "%s - nonzero write interrupt status received: %d\n",
+			 __FUNCTION__, urb->status);
+
+	dev->interrupt_out_busy = 0;
+	wake_up_interruptible(&dev->write_wait);
+}
+
+/**
+ *	ld_usb_open
+ */
+static int ld_usb_open(struct inode *inode, struct file *file)
+{
+	struct ld_usb *dev;
+	int subminor;
+	int retval = 0;
+	struct usb_interface *interface;
+
+	nonseekable_open(inode, file);
+	subminor = iminor(inode);
+
+	down(&disconnect_sem);
+
+	interface = usb_find_interface(&ld_usb_driver, subminor);
+
+	if (!interface) {
+		err("%s - error, can't find device for minor %d\n",
+		     __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;
+
+	/* initialize in direction */
+	dev->ring_head = 0;
+	dev->ring_tail = 0;
+	usb_fill_int_urb(dev->interrupt_in_urb,
+			 interface_to_usbdev(interface),
+			 usb_rcvintpipe(interface_to_usbdev(interface),
+					dev->interrupt_in_endpoint->bEndpointAddress),
+			 dev->interrupt_in_buffer,
+			 dev->interrupt_in_endpoint_size,
+			 ld_usb_interrupt_in_callback,
+			 dev,
+			 dev->interrupt_in_interval);
+
+	dev->interrupt_in_running = 1;
+	dev->interrupt_in_done = 0;
+
+	retval = usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL);
+	if (retval) {
+		dev_err(&interface->dev, "Couldn't submit interrupt_in_urb %d\n", 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);
+
+	return retval;
+}
+
+/**
+ *	ld_usb_release
+ */
+static int ld_usb_release(struct inode *inode, struct file *file)
+{
+	struct ld_usb *dev;
+	int retval = 0;
+
+	dev = file->private_data;
+
+	if (dev == NULL) {
+		retval = -ENODEV;
+		goto exit;
+	}
+
+	if (down_interruptible(&dev->sem)) {
+		retval = -ERESTARTSYS;
+		goto exit;
+	}
+
+	if (dev->open_count != 1) {
+		retval = -ENODEV;
+		goto unlock_exit;
+	}
+	if (dev->intf == NULL) {
+		/* the device was unplugged before the file was released */
+		up(&dev->sem);
+		/* unlock here as ld_usb_delete frees dev */
+		ld_usb_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);
+	ld_usb_abort_transfers(dev);
+	dev->open_count = 0;
+
+unlock_exit:
+	up(&dev->sem);
+
+exit:
+	return retval;
+}
+
+/**
+ *	ld_usb_poll
+ */
+static unsigned int ld_usb_poll(struct file *file, poll_table *wait)
+{
+	struct ld_usb *dev;
+	unsigned int mask = 0;
+
+	dev = file->private_data;
+
+	poll_wait(file, &dev->read_wait, wait);
+	poll_wait(file, &dev->write_wait, wait);
+
+	if (dev->ring_head != dev->ring_tail)
+		mask |= POLLIN | POLLRDNORM;
+	if (!dev->interrupt_out_busy)
+		mask |= POLLOUT | POLLWRNORM;
+
+	return mask;
+}
+
+/**
+ *	ld_usb_read
+ */
+static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
+			   loff_t *ppos)
+{
+	struct ld_usb *dev;
+	size_t *actual_buffer;
+	size_t bytes_to_read;
+	int retval = 0;
+
+	dev = file->private_data;
+
+	/* verify that we actually have some data to read */
+	if (count == 0)
+		goto exit;
+
+	/* lock this object */
+	if (down_interruptible(&dev->sem)) {
+		retval = -ERESTARTSYS;
+		goto exit;
+	}
+
+	/* verify that the device wasn't unplugged */
+	if (dev->intf == NULL) {
+		retval = -ENODEV;
+		err("No device or device unplugged %d\n", retval);
+		goto unlock_exit;
+	}
+
+	/* wait for data */
+	if (dev->ring_head == dev->ring_tail) {
+		if (file->f_flags & O_NONBLOCK) {
+			retval = -EAGAIN;
+			goto unlock_exit;
+		}
+		retval = wait_event_interruptible(dev->read_wait, dev->interrupt_in_done);
+		if (retval < 0)
+			goto unlock_exit;
+	}
+
+	/* actual_buffer contains actual_length + interrupt_in_buffer */
+	actual_buffer = (size_t*)(dev->ring_buffer + dev->ring_tail*(sizeof(size_t)+dev->interrupt_in_endpoint_size));
+	bytes_to_read = min(count, *actual_buffer);
+	if (bytes_to_read < *actual_buffer)
+		dev_warn(&dev->intf->dev, "Read buffer overflow, %d bytes dropped\n",
+			 *actual_buffer-bytes_to_read);
+
+	/* copy one interrupt_in_buffer from ring_buffer into userspace */
+	if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) {
+		retval = -EFAULT;
+		goto unlock_exit;
+	}
+	dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size;
+
+	retval = bytes_to_read;
+
+unlock_exit:
+	/* unlock the device */
+	up(&dev->sem);
+
+exit:
+	return retval;
+}
+
+/**
+ *	ld_usb_write
+ */
+static ssize_t ld_usb_write(struct file *file, const char __user *buffer,
+			    size_t count, loff_t *ppos)
+{
+	struct ld_usb *dev;
+	size_t bytes_to_write;
+	int retval = 0;
+
+	dev = file->private_data;
+
+	/* verify that we actually have some data to write */
+	if (count == 0)
+		goto exit;
+
+	/* lock this object */
+	if (down_interruptible(&dev->sem)) {
+		retval = -ERESTARTSYS;
+		goto exit;
+	}
+
+	/* verify that the device wasn't unplugged */
+	if (dev->intf == NULL) {
+		retval = -ENODEV;
+		err("No device or device unplugged %d\n", retval);
+		goto unlock_exit;
+	}
+
+	/* wait until previous transfer is finished */
+	if (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 < 0) {
+			goto unlock_exit;
+		}
+	}
+
+	/* write the data into interrupt_out_buffer from userspace */
+	bytes_to_write = min(count, write_buffer_size*dev->interrupt_out_endpoint_size);
+	if (bytes_to_write < count)
+		dev_warn(&dev->intf->dev, "Write buffer overflow, %d bytes dropped\n",count-bytes_to_write);
+	dbg_info(&dev->intf->dev, "%s: count = %d, bytes_to_write = %d\n", __FUNCTION__, count, bytes_to_write);
+
+	if (copy_from_user(dev->interrupt_out_buffer, buffer, bytes_to_write)) {
+		retval = -EFAULT;
+		goto unlock_exit;
+	}
+
+	if (dev->interrupt_out_endpoint == NULL) {
+		/* try HID_REQ_SET_REPORT=9 on control_endpoint instead of interrupt_out_endpoint */
+		retval = usb_control_msg(interface_to_usbdev(dev->intf),
+					 usb_sndctrlpipe(interface_to_usbdev(dev->intf), 0),
+					 9,
+					 USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_OUT,
+					 1 << 8, 0,
+					 dev->interrupt_out_buffer,
+					 bytes_to_write,
+					 USB_CTRL_SET_TIMEOUT * HZ);
+		if (retval < 0)
+			err("Couldn't submit HID_REQ_SET_REPORT %d\n", retval);
+		goto unlock_exit;
+	}
+
+	/* send off the urb */
+	usb_fill_int_urb(dev->interrupt_out_urb,
+			 interface_to_usbdev(dev->intf),
+			 usb_sndintpipe(interface_to_usbdev(dev->intf),
+					dev->interrupt_out_endpoint->bEndpointAddress),
+			 dev->interrupt_out_buffer,
+			 bytes_to_write,
+			 ld_usb_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\n", retval);
+		goto unlock_exit;
+	}
+	retval = bytes_to_write;
+
+unlock_exit:
+	/* unlock the device */
+	up(&dev->sem);
+
+exit:
+	return retval;
+}
+
+/* file operations needed when we register this driver */
+static struct file_operations ld_usb_fops = {
+	.owner =	THIS_MODULE,
+	.read  =	ld_usb_read,
+	.write =	ld_usb_write,
+	.open =		ld_usb_open,
+	.release =	ld_usb_release,
+	.poll =		ld_usb_poll,
+};
+
+/*
+ * 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 ld_usb_class = {
+	.name =		"ldusb%d",
+	.fops =		&ld_usb_fops,
+	.minor_base =	USB_LD_MINOR_BASE,
+};
+
+/**
+ *	ld_usb_probe
+ *
+ *	Called by the usb core when a new device is connected that it thinks
+ *	this driver might be interested in.
+ */
+static int ld_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(intf);
+	struct ld_usb *dev = NULL;
+	struct usb_host_interface *iface_desc;
+	struct usb_endpoint_descriptor *endpoint;
+	char *buffer;
+	int i;
+	int retval = -ENOMEM;
+
+	/* allocate memory for our device state and intialize it */
+
+	dev = kmalloc(sizeof(*dev), GFP_KERNEL);
+	if (dev == NULL) {
+		dev_err(&intf->dev, "Out of memory\n");
+		goto exit;
+	}
+	memset(dev, 0x00, sizeof(*dev));
+	init_MUTEX(&dev->sem);
+	dev->intf = intf;
+	init_waitqueue_head(&dev->read_wait);
+	init_waitqueue_head(&dev->write_wait);
+
+	/* workaround for early firmware versions on fast computers */
+	if ((le16_to_cpu(udev->descriptor.idVendor) == USB_VENDOR_ID_LD) &&
+	    ((le16_to_cpu(udev->descriptor.idProduct) == USB_DEVICE_ID_CASSY) ||
+	     (le16_to_cpu(udev->descriptor.idProduct) == USB_DEVICE_ID_COM3LAB)) &&
+	    (le16_to_cpu(udev->descriptor.bcdDevice) <= 0x103)) {
+		buffer = kmalloc(256, GFP_KERNEL);
+		/* usb_string makes SETUP+STALL to leave always ControlReadLoop */
+		usb_string(udev, 255, buffer, 256);
+		kfree(buffer);
+	}
+
+	iface_desc = intf->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) {
+		dev_err(&intf->dev, "Interrupt in endpoint not found\n");
+		goto error;
+	}
+	if (dev->interrupt_out_endpoint == NULL)
+		dev_warn(&intf->dev, "Interrupt out endpoint not found (using control endpoint instead)\n");
+
+	dev->interrupt_in_endpoint_size = le16_to_cpu(dev->interrupt_in_endpoint->wMaxPacketSize);
+	dev->ring_buffer = kmalloc(ring_buffer_size*(sizeof(size_t)+dev->interrupt_in_endpoint_size), GFP_KERNEL);
+	if (!dev->ring_buffer) {
+		dev_err(&intf->dev, "Couldn't allocate ring_buffer\n");
+		goto error;
+	}
+	dev->interrupt_in_buffer = kmalloc(dev->interrupt_in_endpoint_size, GFP_KERNEL);
+	if (!dev->interrupt_in_buffer) {
+		dev_err(&intf->dev, "Couldn't allocate interrupt_in_buffer\n");
+		goto error;
+	}
+	dev->interrupt_in_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!dev->interrupt_in_urb) {
+		dev_err(&intf->dev, "Couldn't allocate interrupt_in_urb\n");
+		goto error;
+	}
+	dev->interrupt_out_endpoint_size = dev->interrupt_out_endpoint ? le16_to_cpu(dev->interrupt_out_endpoint->wMaxPacketSize) :
+									 udev->descriptor.bMaxPacketSize0;
+	dev->interrupt_out_buffer = kmalloc(write_buffer_size*dev->interrupt_out_endpoint_size, GFP_KERNEL);
+	if (!dev->interrupt_out_buffer) {
+		dev_err(&intf->dev, "Couldn't allocate interrupt_out_buffer\n");
+		goto error;
+	}
+	dev->interrupt_out_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!dev->interrupt_out_urb) {
+		dev_err(&intf->dev, "Couldn't allocate interrupt_out_urb\n");
+		goto error;
+	}
+	dev->interrupt_in_interval = min_interrupt_in_interval > dev->interrupt_in_endpoint->bInterval ? min_interrupt_in_interval : dev->interrupt_in_endpoint->bInterval;
+	if (dev->interrupt_out_endpoint)
+		dev->interrupt_out_interval = min_interrupt_out_interval > dev->interrupt_out_endpoint->bInterval ? min_interrupt_out_interval : dev->interrupt_out_endpoint->bInterval;
+
+	/* we can register the device now, as it is ready */
+	usb_set_intfdata(intf, dev);
+
+	retval = usb_register_dev(intf, &ld_usb_class);
+	if (retval) {
+		/* something prevented us from registering this driver */
+		dev_err(&intf->dev, "Not able to get a minor for this device.\n");
+		usb_set_intfdata(intf, NULL);
+		goto error;
+	}
+
+	/* let the user know what node this device is now attached to */
+	dev_info(&intf->dev, "LD USB Device #%d now attached to major %d minor %d\n",
+		(intf->minor - USB_LD_MINOR_BASE), USB_MAJOR, intf->minor);
+
+exit:
+	return retval;
+
+error:
+	ld_usb_delete(dev);
+
+	return retval;
+}
+
+/**
+ *	ld_usb_disconnect
+ *
+ *	Called by the usb core when the device is removed from the system.
+ */
+static void ld_usb_disconnect(struct usb_interface *intf)
+{
+	struct ld_usb *dev;
+	int minor;
+
+	down(&disconnect_sem);
+
+	dev = usb_get_intfdata(intf);
+	usb_set_intfdata(intf, NULL);
+
+	down(&dev->sem);
+
+	minor = intf->minor;
+
+	/* give back our minor */
+	usb_deregister_dev(intf, &ld_usb_class);
+
+	/* if the device is not opened, then we clean up right now */
+	if (!dev->open_count) {
+		up(&dev->sem);
+		ld_usb_delete(dev);
+	} else {
+		dev->intf = NULL;
+		up(&dev->sem);
+	}
+
+	up(&disconnect_sem);
+
+	dev_info(&intf->dev, "LD USB Device #%d now disconnected\n",
+		 (minor - USB_LD_MINOR_BASE));
+}
+
+/* usb specific object needed to register this driver with the usb subsystem */
+static struct usb_driver ld_usb_driver = {
+	.owner =	THIS_MODULE,
+	.name =		"ldusb",
+	.probe =	ld_usb_probe,
+	.disconnect =	ld_usb_disconnect,
+	.id_table =	ld_usb_table,
+};
+
+/**
+ *	ld_usb_init
+ */
+static int __init ld_usb_init(void)
+{
+	int retval;
+
+	/* register this driver with the USB subsystem */
+	retval = usb_register(&ld_usb_driver);
+	if (retval)
+		err("usb_register failed for the "__FILE__" driver. Error number %d\n", retval);
+
+	return retval;
+}
+
+/**
+ *	ld_usb_exit
+ */
+static void __exit ld_usb_exit(void)
+{
+	/* deregister this driver with the USB subsystem */
+	usb_deregister(&ld_usb_driver);
+}
+
+module_init(ld_usb_init);
+module_exit(ld_usb_exit);
+