/*
 * USB Skeleton driver - 0.7
 *
 * Copyright (C) 2001 Greg Kroah-Hartman (greg@kroah.com)
 *
 *      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.
 *
 *
 * This driver is to be used as a skeleton driver to be able to create a
 * USB driver quickly.  The design of it is based on the usb-serial and
 * dc2xx drivers.
 *
 * Thanks to Oliver Neukum and David Brownell for their help in debugging
 * this driver.
 *
 * TODO:
 *      - fix urb->status race condition in write sequence
 *      - move minor_table to a dynamic list.
 *
 * History:
 *
 * 2002_02_12 - 0.7 - zero out dev in probe function for devices that do
 *                      not have both a bulk in and bulk out endpoint.
 *                      Thanks to Holger Waechtler for the fix.
 * 2001_11_05 - 0.6 - fix minor locking problem in skel_disconnect.
 *                      Thanks to Pete Zaitcev for the fix.
 * 2001_09_04 - 0.5 - fix devfs bug in skel_disconnect. Thanks to wim delvaux
 * 2001_08_21 - 0.4 - more small bug fixes.
 * 2001_05_29 - 0.3 - more bug fixes based on review from linux-usb-devel
 * 2001_05_24 - 0.2 - bug fixes based on review from linux-usb-devel people
 * 2001_05_01 - 0.1 - first version
 * 
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fcntl.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <linux/smp_lock.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/usb.h>

#ifdef CONFIG_USB_DEBUG
        static int debug = 1;
#else
        static int debug;
#endif

/* Use our own dbg macro */
#undef dbg
#define dbg(format, arg...) do { if (debug) printk(KERN_DEBUG __FILE__ ": " format "\n" , ## arg); } while (0)


/* Version Information */
#define DRIVER_VERSION "v0.4"
#define DRIVER_AUTHOR "Greg Kroah-Hartman, greg@kroah.com"
#define DRIVER_DESC "USB Skeleton Driver"

/* Module paramaters */
MODULE_PARM(debug, "i");
MODULE_PARM_DESC(debug, "Debug enabled or not");


/* Define these values to match your device */
#define USB_SKEL_VENDOR_ID      0xfff0
#define USB_SKEL_PRODUCT_ID     0xfff0

/* table of devices that work with this driver */
static struct usb_device_id skel_table [] = {
        { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
        { }                                     /* Terminating entry */
};

MODULE_DEVICE_TABLE (usb, skel_table);



/* Get a minor range for your devices from the usb maintainer */
#define USB_SKEL_MINOR_BASE     192     

/* we can have up to this number of device plugged in at once */
#define MAX_DEVICES             16

/* Structure to hold all of our device specific stuff */
struct usb_skel {
        struct usb_device *     udev;                   /* save off the usb device pointer */
        struct usb_interface *  interface;              /* the interface for this device */
        devfs_handle_t          devfs;                  /* devfs device node */
        unsigned char           minor;                  /* the starting minor number for this device */
        unsigned char           num_ports;              /* the number of ports this device has */
        char                    num_interrupt_in;       /* number of interrupt in endpoints we have */
        char                    num_bulk_in;            /* number of bulk in endpoints we have */
        char                    num_bulk_out;           /* number of bulk out endpoints we have */

        unsigned char *         bulk_in_buffer;         /* the buffer to receive data */
        int                     bulk_in_size;           /* the size of the receive buffer */
        __u8                    bulk_in_endpointAddr;   /* the address of the bulk in endpoint */

        unsigned char *         bulk_out_buffer;        /* the buffer to send data */
        int                     bulk_out_size;          /* the size of the send buffer */
        struct urb *            write_urb;              /* the urb used to send data */
        __u8                    bulk_out_endpointAddr;  /* the address of the bulk out endpoint */

        struct tq_struct        tqueue;                 /* task queue for line discipline waking up */
        int                     open_count;             /* number of times this port has been opened */
        struct semaphore        sem;                    /* locks this structure */
};


/* the global usb devfs handle */
extern devfs_handle_t usb_devfs_handle;


/* local function prototypes */
static ssize_t skel_read        (struct file *file, char *buffer, size_t count, loff_t *ppos);
static ssize_t skel_write       (struct file *file, const char *buffer, size_t count, loff_t *ppos);
static int skel_ioctl           (struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg);
static int skel_open            (struct inode *inode, struct file *file);
static int skel_release         (struct inode *inode, struct file *file);
        
static void * skel_probe        (struct usb_device *dev, unsigned int ifnum, const struct usb_device_id *id);
static void skel_disconnect     (struct usb_device *dev, void *ptr);

static void skel_write_bulk_callback    (struct urb *urb);


/* array of pointers to our devices that are currently connected */
static struct usb_skel          *minor_table[MAX_DEVICES];

/* lock to protect the minor_table structure */
static DECLARE_MUTEX (minor_table_mutex);

/*
 * File operations needed when we register this driver.
 * This assumes that this driver NEEDS file operations,
 * of course, which means that the driver is expected
 * to have a node in the /dev directory. If the USB
 * device were for a network interface then the driver
 * would use "struct net_driver" instead, and a serial
 * device would use "struct tty_driver". 
 */
static struct file_operations skel_fops = {
        /*
         * The owner field is part of the module-locking
         * mechanism. The idea is that the kernel knows
         * which module to increment the use-counter of
         * BEFORE it calls the device's open() function.
         * This also means that the kernel can decrement
         * the use-counter again before calling release()
         * or should the open() function fail.
         *
         * Not all device structures have an "owner" field
         * yet. "struct file_operations" and "struct net_device"
         * do, while "struct tty_driver" does not. If the struct
         * has an "owner" field, then initialize it to the value
         * THIS_MODULE and the kernel will handle all module
         * locking for you automatically. Otherwise, you must
         * increment the use-counter in the open() function
         * and decrement it again in the release() function
         * yourself.
         */
        owner:          THIS_MODULE,

        read:           skel_read,
        write:          skel_write,
        ioctl:          skel_ioctl,
        open:           skel_open,
        release:        skel_release,
};      


/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver skel_driver = {
        name:           "skeleton",
        probe:          skel_probe,
        disconnect:     skel_disconnect,
        fops:           &skel_fops,
        minor:          USB_SKEL_MINOR_BASE,
        id_table:       skel_table,
};





/**
 *      usb_skel_debug_data
 */
static inline void usb_skel_debug_data (const char *function, int size, const unsigned char *data)
{
        int i;

        if (!debug)
                return;
        
        printk (KERN_DEBUG __FILE__": %s - length = %d, data = ", 
                function, size);
        for (i = 0; i < size; ++i) {
                printk ("%.2x ", data[i]);
        }
        printk ("\n");
}


/**
 *      skel_delete
 */
static inline void skel_delete (struct usb_skel *dev)
{
        minor_table[dev->minor] = NULL;
        if (dev->bulk_in_buffer != NULL)
                kfree (dev->bulk_in_buffer);
        if (dev->bulk_out_buffer != NULL)
                kfree (dev->bulk_out_buffer);
        if (dev->write_urb != NULL)
                usb_free_urb (dev->write_urb);
        kfree (dev);
}


/**
 *      skel_open
 */
static int skel_open (struct inode *inode, struct file *file)
{
        struct usb_skel *dev = NULL;
        int subminor;
        int retval = 0;
        
        dbg(__FUNCTION__);

        subminor = MINOR (inode->i_rdev) - USB_SKEL_MINOR_BASE;
        if ((subminor < 0) ||
            (subminor >= MAX_DEVICES)) {
                return -ENODEV;
        }

        /* Increment our usage count for the module.
         * This is redundant here, because "struct file_operations"
         * has an "owner" field. This line is included here soley as
         * a reference for drivers using lesser structures... ;-)
         */
        MOD_INC_USE_COUNT;

        /* lock our minor table and get our local data for this minor */
        down (&minor_table_mutex);
        dev = minor_table[subminor];
        if (dev == NULL) {
                up (&minor_table_mutex);
                MOD_DEC_USE_COUNT;
                return -ENODEV;
        }

        /* lock this device */
        down (&dev->sem);

        /* unlock the minor table */
        up (&minor_table_mutex);

        /* increment our usage count for the driver */
        ++dev->open_count;

        /* save our object in the file's private structure */
        file->private_data = dev;

        /* unlock this device */
        up (&dev->sem);

        return retval;
}


/**
 *      skel_release
 */
static int skel_release (struct inode *inode, struct file *file)
{
        struct usb_skel *dev;
        int retval = 0;

        dev = (struct usb_skel *)file->private_data;
        if (dev == NULL) {
                dbg (__FUNCTION__ " - object is NULL");
                return -ENODEV;
        }

        dbg(__FUNCTION__ " - minor %d", dev->minor);

        /* lock our minor table */
        down (&minor_table_mutex);

        /* lock our device */
        down (&dev->sem);

        if (dev->open_count <= 0) {
                dbg (__FUNCTION__ " - device not opened");
                retval = -ENODEV;
                goto exit_not_opened;
        }

        if (dev->udev == NULL) {
                /* the device was unplugged before the file was released */
                up (&dev->sem);
                skel_delete (dev);
                up (&minor_table_mutex);
                MOD_DEC_USE_COUNT;
                return 0;
        }

        /* decrement our usage count for the device */
        --dev->open_count;
        if (dev->open_count <= 0) {
                /* shutdown any bulk writes that might be going on */
                usb_unlink_urb (dev->write_urb);
                dev->open_count = 0;
        }

        /* decrement our usage count for the module */
        MOD_DEC_USE_COUNT;

exit_not_opened:
        up (&dev->sem);
        up (&minor_table_mutex);

        return retval;
}


/**
 *      skel_read
 */
static ssize_t skel_read (struct file *file, char *buffer, size_t count, loff_t *ppos)
{
        struct usb_skel *dev;
        int retval = 0;

        dev = (struct usb_skel *)file->private_data;
        
        dbg(__FUNCTION__ " - minor %d, count = %d", dev->minor, count);

        /* lock this object */
        down (&dev->sem);

        /* verify that the device wasn't unplugged */
        if (dev->udev == NULL) {
                up (&dev->sem);
                return -ENODEV;
        }
        
        /* do an immediate bulk read to get data from the device */
        retval = usb_bulk_msg (dev->udev,
                               usb_rcvbulkpipe (dev->udev, 
                                                dev->bulk_in_endpointAddr),
                               dev->bulk_in_buffer, dev->bulk_in_size,
                               &count, HZ*10);

        /* if the read was successful, copy the data to userspace */
        if (!retval) {
                if (copy_to_user (buffer, dev->bulk_in_buffer, count))
                        retval = -EFAULT;
                else
                        retval = count;
        }
        
        /* unlock the device */
        up (&dev->sem);
        return retval;
}


/**
 *      skel_write
 */
static ssize_t skel_write (struct file *file, const char *buffer, size_t count, loff_t *ppos)
{
        struct usb_skel *dev;
        ssize_t bytes_written = 0;
        int retval = 0;

        dev = (struct usb_skel *)file->private_data;

        dbg(__FUNCTION__ " - minor %d, count = %d", dev->minor, count);

        /* lock this object */
        down (&dev->sem);

        /* verify that the device wasn't unplugged */
        if (dev->udev == NULL) {
                retval = -ENODEV;
                goto exit;
        }

        /* verify that we actually have some data to write */
        if (count == 0) {
                dbg(__FUNCTION__ " - write request of 0 bytes");
                goto exit;
        }

        /* see if we are already in the middle of a write */
        if (dev->write_urb->status == -EINPROGRESS) {
                dbg (__FUNCTION__ " - already writing");
                goto exit;
        }

        /* we can only write as much as 1 urb will hold */
        bytes_written = (count > dev->bulk_out_size) ? 
                                dev->bulk_out_size : count;

        /* copy the data from userspace into our urb */
        if (copy_from_user(dev->write_urb->transfer_buffer, buffer, 
                           bytes_written)) {
                retval = -EFAULT;
                goto exit;
        }

        usb_skel_debug_data (__FUNCTION__, bytes_written, 
                             dev->write_urb->transfer_buffer);

        /* set up our urb */
        FILL_BULK_URB(dev->write_urb, dev->udev, 
                      usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
                      dev->write_urb->transfer_buffer, bytes_written,
                      skel_write_bulk_callback, dev);

        /* send the data out the bulk port */
        retval = usb_submit_urb(dev->write_urb);
        if (retval) {
                err(__FUNCTION__ " - failed submitting write urb, error %d",
                    retval);
        } else {
                retval = bytes_written;
        }

exit:
        /* unlock the device */
        up (&dev->sem);

        return retval;
}


/**
 *      skel_ioctl
 */
static int skel_ioctl (struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
        struct usb_skel *dev;

        dev = (struct usb_skel *)file->private_data;

        /* lock this object */
        down (&dev->sem);

        /* verify that the device wasn't unplugged */
        if (dev->udev == NULL) {
                up (&dev->sem);
                return -ENODEV;
        }

        dbg(__FUNCTION__ " - minor %d, cmd 0x%.4x, arg %ld", 
            dev->minor, cmd, arg);


        /* fill in your device specific stuff here */
        
        /* unlock the device */
        up (&dev->sem);
        
        /* return that we did not understand this ioctl call */
        return -ENOTTY;
}


/**
 *      skel_write_bulk_callback
 */
static void skel_write_bulk_callback (struct urb *urb)
{
        struct usb_skel *dev = (struct usb_skel *)urb->context;

        dbg(__FUNCTION__ " - minor %d", dev->minor);

        if ((urb->status != -ENOENT) && 
            (urb->status != -ECONNRESET)) {
                dbg(__FUNCTION__ " - nonzero write bulk status received: %d",
                    urb->status);
                return;
        }

        return;
}


/**
 *      skel_probe
 *
 *      Called by the usb core when a new device is connected that it thinks
 *      this driver might be interested in.
 */
static void * skel_probe(struct usb_device *udev, unsigned int ifnum, const struct usb_device_id *id)
{
        struct usb_skel *dev = NULL;
        struct usb_interface *interface;
        struct usb_interface_descriptor *iface_desc;
        struct usb_endpoint_descriptor *endpoint;
        int minor;
        int buffer_size;
        int i;
        char name[10];

        
        /* See if the device offered us matches what we can accept */
        if ((udev->descriptor.idVendor != USB_SKEL_VENDOR_ID) ||
            (udev->descriptor.idProduct != USB_SKEL_PRODUCT_ID)) {
                return NULL;
        }

        /* select a "subminor" number (part of a minor number) */
        down (&minor_table_mutex);
        for (minor = 0; minor < MAX_DEVICES; ++minor) {
                if (minor_table[minor] == NULL)
                        break;
        }
        if (minor >= MAX_DEVICES) {
                info ("Too many devices plugged in, can not handle this device.");
                goto exit;
        }

        /* allocate memory for our device state and intialize it */
        dev = kmalloc (sizeof(struct usb_skel), GFP_KERNEL);
        if (dev == NULL) {
                err ("Out of memory");
                goto exit;
        }
        memset (dev, 0x00, sizeof (*dev));
        minor_table[minor] = dev;

        interface = &udev->actconfig->interface[ifnum];

        init_MUTEX (&dev->sem);
        dev->udev = udev;
        dev->interface = interface;
        dev->minor = minor;

        /* set up the endpoint information */
        /* check out the endpoints */
        iface_desc = &interface->altsetting[0];
        for (i = 0; i < iface_desc->bNumEndpoints; ++i) {
                endpoint = &iface_desc->endpoint[i];

                if ((endpoint->bEndpointAddress & 0x80) &&
                    ((endpoint->bmAttributes & 3) == 0x02)) {
                        /* we found a bulk in endpoint */
                        buffer_size = endpoint->wMaxPacketSize;
                        dev->bulk_in_size = buffer_size;
                        dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
                        dev->bulk_in_buffer = kmalloc (buffer_size, GFP_KERNEL);
                        if (!dev->bulk_in_buffer) {
                                err("Couldn't allocate bulk_in_buffer");
                                goto error;
                        }
                }
                
                if (((endpoint->bEndpointAddress & 0x80) == 0x00) &&
                    ((endpoint->bmAttributes & 3) == 0x02)) {
                        /* we found a bulk out endpoint */
                        dev->write_urb = usb_alloc_urb(0);
                        if (!dev->write_urb) {
                                err("No free urbs available");
                                goto error;
                        }
                        buffer_size = endpoint->wMaxPacketSize;
                        dev->bulk_out_size = buffer_size;
                        dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
                        dev->bulk_out_buffer = kmalloc (buffer_size, GFP_KERNEL);
                        if (!dev->bulk_out_buffer) {
                                err("Couldn't allocate bulk_out_buffer");
                                goto error;
                        }
                        FILL_BULK_URB(dev->write_urb, udev, 
                                      usb_sndbulkpipe(udev, 
                                                      endpoint->bEndpointAddress),
                                      dev->bulk_out_buffer, buffer_size,
                                      skel_write_bulk_callback, dev);
                }
        }

        /* initialize the devfs node for this device and register it */
        sprintf(name, "skel%d", dev->minor);
        
        dev->devfs = devfs_register (usb_devfs_handle, name,
                                     DEVFS_FL_DEFAULT, USB_MAJOR,
                                     USB_SKEL_MINOR_BASE + dev->minor,
                                     S_IFCHR | S_IRUSR | S_IWUSR | 
                                     S_IRGRP | S_IWGRP | S_IROTH, 
                                     &skel_fops, NULL);

        /* let the user know what node this device is now attached to */
        info ("USB Skeleton device now attached to USBSkel%d", dev->minor);
        goto exit;
        
error:
        skel_delete (dev);
        dev = NULL;

exit:
        up (&minor_table_mutex);
        return dev;
}


/**
 *      skel_disconnect
 *
 *      Called by the usb core when the device is removed from the system.
 */
static void skel_disconnect(struct usb_device *udev, void *ptr)
{
        struct usb_skel *dev;
        int minor;

        dev = (struct usb_skel *)ptr;
        
        down (&minor_table_mutex);
        down (&dev->sem);
                
        minor = dev->minor;

        /* remove our devfs node */
        devfs_unregister(dev->devfs);

        /* if the device is not opened, then we clean up right now */
        if (!dev->open_count) {
                up (&dev->sem);
                skel_delete (dev);
        } else {
                dev->udev = NULL;
                up (&dev->sem);
        }

        info("USB Skeleton #%d now disconnected", minor);
        up (&minor_table_mutex);
}



/**
 *      usb_skel_init
 */
static int __init usb_skel_init(void)
{
        int result;

        /* register this driver with the USB subsystem */
        result = usb_register(&skel_driver);
        if (result < 0) {
                err("usb_register failed for the "__FILE__" driver. Error number %d",
                    result);
                return -1;
        }

        info(DRIVER_DESC " " DRIVER_VERSION);
        return 0;
}


/**
 *      usb_skel_exit
 */
static void __exit usb_skel_exit(void)
{
        /* deregister this driver with the USB subsystem */
        usb_deregister(&skel_driver);
}


module_init (usb_skel_init);
module_exit (usb_skel_exit);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");