usb-skeleton.c

/*
 * USB Skeleton driver - 2.0
 *
 * Copyright (C) 2001-2004 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, version 2.
 *
 * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c 
 * but has been rewritten to be easy to read and use, as no locks are now
 * needed anymore.
 *
 */

#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/kref.h>
#include <linux/smp_lock.h>
#include <linux/usb.h>
#include <asm/uaccess.h>


/* Define these values to match your devices */
#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

/* Structure to hold all of our device specific stuff */
struct usb_skel {
    struct usb_device * udev;           /* the usb device for this device */
    struct usb_interface *  interface;      /* the interface for this device */
    unsigned char *     bulk_in_buffer;     /* the buffer to receive data */
    size_t          bulk_in_size;       /* the size of the receive buffer */
    __u8            bulk_in_endpointAddr;   /* the address of the bulk in endpoint */
    __u8            bulk_out_endpointAddr;  /* the address of the bulk out endpoint */
    struct kref     kref;
};
#define to_skel_dev(d) container_of(d, struct usb_skel, kref)

static struct usb_driver skel_driver;

static void skel_delete(struct kref *kref)
{   
    struct usb_skel *dev = to_skel_dev(kref);

    usb_put_dev(dev->udev);
    kfree (dev->bulk_in_buffer);
    kfree (dev);
}

static int skel_open(struct inode *inode, struct file *file)
{
    struct usb_skel *dev;
    struct usb_interface *interface;
    int subminor;
    int retval = 0;

    subminor = iminor(inode);

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

    dev = usb_get_intfdata(interface);
    if (!dev) {
        retval = -ENODEV;
        goto exit;
    }
    
    /* increment our usage count for the device */
    kref_get(&dev->kref);

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

exit:
    return retval;
}

static int skel_release(struct inode *inode, struct file *file)
{
    struct usb_skel *dev;

    dev = (struct usb_skel *)file->private_data;
    if (dev == NULL)
        return -ENODEV;

    /* decrement the count on our device */
    kref_put(&dev->kref, skel_delete);
    return 0;
}

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

    dev = (struct usb_skel *)file->private_data;
    
    /* do a blocking 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,
                  min(dev->bulk_in_size, count),
                  &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;
    }

    return retval;
}

static void skel_write_bulk_callback(struct urb *urb, struct pt_regs *regs)
{
    /* sync/async unlink faults aren't errors */
    if (urb->status && 
        !(urb->status == -ENOENT || 
          urb->status == -ECONNRESET ||
          urb->status == -ESHUTDOWN)) {
        dbg("%s - nonzero write bulk status received: %d",
            __FUNCTION__, urb->status);
    }

    /* free up our allocated buffer */
    usb_buffer_free(urb->dev, urb->transfer_buffer_length, 
            urb->transfer_buffer, urb->transfer_dma);
}

static ssize_t skel_write(struct file *file, const char __user *user_buffer, size_t count, loff_t *ppos)
{
    struct usb_skel *dev;
    int retval = 0;
    struct urb *urb = NULL;
    char *buf = NULL;

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

    /* verify that we actually have some data to write */
    if (count == 0)
        goto exit;

    /* create a urb, and a buffer for it, and copy the data to the urb */
    urb = usb_alloc_urb(0, GFP_KERNEL);
    if (!urb) {
        retval = -ENOMEM;
        goto error;
    }

    buf = usb_buffer_alloc(dev->udev, count, GFP_KERNEL, &urb->transfer_dma);
    if (!buf) {
        retval = -ENOMEM;
        goto error;
    }
    if (copy_from_user(buf, user_buffer, count)) {
        retval = -EFAULT;
        goto error;
    }

    /* initialize the urb properly */
    usb_fill_bulk_urb(urb, dev->udev,
              usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
              buf, count, skel_write_bulk_callback, dev);
    urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

    /* send the data out the bulk port */
    retval = usb_submit_urb(urb, GFP_KERNEL);
    if (retval) {
        err("%s - failed submitting write urb, error %d", __FUNCTION__, retval);
        goto error;
    }

    /* release our reference to this urb, the USB core will eventually free it entirely */
    usb_free_urb(urb);

exit:
    return count;

error:
    usb_buffer_free(dev->udev, count, buf, urb->transfer_dma);
    usb_free_urb(urb);
    kfree(buf);
    return retval;
}

static struct file_operations skel_fops = {
    .owner =    THIS_MODULE,
    .read =     skel_read,
    .write =    skel_write,
    .open =     skel_open,
    .release =  skel_release,
};

/* 
 * 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 skel_class = {
    .name = "usb/skel%d",
    .fops = &skel_fops,
    .mode = S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH,
    .minor_base = USB_SKEL_MINOR_BASE,
};

static int skel_probe(struct usb_interface *interface, const struct usb_device_id *id)
{
    struct usb_skel *dev = NULL;
    struct usb_host_interface *iface_desc;
    struct usb_endpoint_descriptor *endpoint;
    size_t buffer_size;
    int i;
    int retval = -ENOMEM;

    /* allocate memory for our device state and initialize it */
    dev = kmalloc(sizeof(struct usb_skel), GFP_KERNEL);
    if (dev == NULL) {
        err("Out of memory");
        goto error;
    }
    memset(dev, 0x00, sizeof (*dev));
    kref_init(&dev->kref);

    dev->udev = usb_get_dev(interface_to_usbdev(interface));
    dev->interface = interface;

    /* set up the endpoint information */
    /* use only the first bulk-in and bulk-out endpoints */
    iface_desc = interface->cur_altsetting;
    for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
        endpoint = &iface_desc->endpoint[i].desc;

        if (!dev->bulk_in_endpointAddr &&
            (endpoint->bEndpointAddress & USB_DIR_IN) &&
            ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
                    == USB_ENDPOINT_XFER_BULK)) {
            /* 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("Could not allocate bulk_in_buffer");
                goto error;
            }
        }

        if (!dev->bulk_out_endpointAddr &&
            !(endpoint->bEndpointAddress & USB_DIR_IN) &&
            ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
                    == USB_ENDPOINT_XFER_BULK)) {
            /* we found a bulk out endpoint */
            dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
        }
    }
    if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
        err("Could not find both bulk-in and bulk-out endpoints");
        goto error;
    }

    /* save our data pointer in this interface device */
    usb_set_intfdata(interface, dev);

    /* we can register the device now, as it is ready */
    retval = usb_register_dev(interface, &skel_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;
    }

    /* let the user know what node this device is now attached to */
    info("USB Skeleton device now attached to USBSkel-%d", interface->minor);
    return 0;

error:
    if (dev)
        kref_put(&dev->kref, skel_delete);
    return retval;
}

static void skel_disconnect(struct usb_interface *interface)
{
    struct usb_skel *dev;
    int minor = interface->minor;

    /* prevent skel_open() from racing skel_disconnect() */
    lock_kernel();

    dev = usb_get_intfdata(interface);
    usb_set_intfdata(interface, NULL);

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

    unlock_kernel();

    /* decrement our usage count */
    kref_put(&dev->kref, skel_delete);

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

static struct usb_driver skel_driver = {
    .owner = THIS_MODULE,
    .name = "skeleton",
    .id_table = skel_table,
    .probe = skel_probe,
    .disconnect = skel_disconnect,
};

static int __init usb_skel_init(void)
{
    int result;

    /* register this driver with the USB subsystem */
    result = usb_register(&skel_driver);
    if (result)
        err("usb_register failed. Error number %d", result);

    return result;
}

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_LICENSE("GPL");