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legousbtower.c

/*
 * 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/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/mutex.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);
static DEFINE_MUTEX(open_disc_mutex);

#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);
static void tower_interrupt_out_callback (struct urb *urb);

static int  tower_probe (struct usb_interface *interface, const struct usb_device_id *id);
static void tower_disconnect  (struct usb_interface *interface);


/* file operations needed when we register this driver */
static const 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 the driver core
 */
static struct usb_class_driver tower_class = {
      .name =           "legousbtower%d",
      .fops =           &tower_fops,
      .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 = {
      .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 */
      usb_free_urb(dev->interrupt_in_urb);
      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);

      interface = usb_find_interface (&tower_driver, subminor);

      if (!interface) {
            err ("%s - error, can't find device for minor %d",
                 __FUNCTION__, subminor);
            retval = -ENODEV;
            goto exit;
      }

      mutex_lock(&open_disc_mutex);
      dev = usb_get_intfdata(interface);

      if (!dev) {
            mutex_unlock(&open_disc_mutex);
            retval = -ENODEV;
            goto exit;
      }

      /* lock this device */
      if (down_interruptible (&dev->sem)) {
            mutex_unlock(&open_disc_mutex);
              retval = -ERESTARTSYS;
            goto exit;
      }


      /* allow opening only once */
      if (dev->open_count) {
            mutex_unlock(&open_disc_mutex);
            retval = -EBUSY;
            goto unlock_exit;
      }
      dev->open_count = 1;
      mutex_unlock(&open_disc_mutex);

      /* 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);

exit:
      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_nolock;
      }

      mutex_lock(&open_disc_mutex);
      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:
      mutex_unlock(&open_disc_mutex);
exit_nolock:
      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->udev)
                  usb_kill_urb (dev->interrupt_in_urb);
      }
      if (dev->interrupt_out_busy && 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 lego_usb_tower *dev = (struct lego_usb_tower *)urb->context;
      int status = urb->status;
      int retval;

      dbg(4, "%s: enter, status %d", __FUNCTION__, status);

      lego_usb_tower_debug_data(5, __FUNCTION__, urb->actual_length, urb->transfer_buffer);

      if (status) {
            if (status == -ENOENT ||
                status == -ECONNRESET ||
                status == -ESHUTDOWN) {
                  goto exit;
            } else {
                  dbg(1, "%s: nonzero status received: %d", __FUNCTION__, 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__, status);
}


/**
 *    tower_interrupt_out_callback
 */
static void tower_interrupt_out_callback (struct urb *urb)
{
      struct lego_usb_tower *dev = (struct lego_usb_tower *)urb->context;
      int status = urb->status;

      dbg(4, "%s: enter, status %d", __FUNCTION__, status);
      lego_usb_tower_debug_data(5, __FUNCTION__, urb->actual_length, urb->transfer_buffer);

      /* sync/async unlink faults aren't errors */
      if (status && !(status == -ENOENT ||
                  status == -ECONNRESET ||
                  status == -ESHUTDOWN)) {
            dbg(1, "%s - nonzero write bulk status received: %d",
                __FUNCTION__, 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__, 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 initialize 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 (usb_endpoint_xfer_int(endpoint)) {
                  if (usb_endpoint_dir_in(endpoint))
                        dev->interrupt_in_endpoint = endpoint;
                  else
                        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__);

      dev = usb_get_intfdata (interface);
      mutex_lock(&open_disc_mutex);
      usb_set_intfdata (interface, NULL);

      minor = dev->minor;

      /* give back our minor */
      usb_deregister_dev (interface, &tower_class);

      down (&dev->sem);
      mutex_unlock(&open_disc_mutex);

      /* 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);
      }

      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

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