file.c

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/*
 * drivers/usb/core/file.c
 *
 * (C) Copyright Linus Torvalds 1999
 * (C) Copyright Johannes Erdfelt 1999-2001
 * (C) Copyright Andreas Gal 1999
 * (C) Copyright Gregory P. Smith 1999
 * (C) Copyright Deti Fliegl 1999 (new USB architecture)
 * (C) Copyright Randy Dunlap 2000
 * (C) Copyright David Brownell 2000-2001 (kernel hotplug, usb_device_id,
    more docs, etc)
 * (C) Copyright Yggdrasil Computing, Inc. 2000
 *     (usb_device_id matching changes by Adam J. Richter)
 * (C) Copyright Greg Kroah-Hartman 2002-2003
 *
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/usb.h>

#include "usb.h"

#define MAX_USB_MINORS  256
static const struct file_operations *usb_minors[MAX_USB_MINORS];
static DECLARE_RWSEM(minor_rwsem);

static int usb_open(struct inode * inode, struct file * file)
{
    int minor = iminor(inode);
    const struct file_operations *c;
    int err = -ENODEV;
    const struct file_operations *old_fops, *new_fops = NULL;

    down_read(&minor_rwsem);
    c = usb_minors[minor];

    if (!c || !(new_fops = fops_get(c)))
        goto done;

    old_fops = file->f_op;
    file->f_op = new_fops;
    /* Curiouser and curiouser... NULL ->open() as "no device" ? */
    if (file->f_op->open)
        err = file->f_op->open(inode,file);
    if (err) {
        fops_put(file->f_op);
        file->f_op = fops_get(old_fops);
    }
    fops_put(old_fops);
 done:
    up_read(&minor_rwsem);
    return err;
}

static const struct file_operations usb_fops = {
    .owner =    THIS_MODULE,
    .open =     usb_open,
    .llseek =   noop_llseek,
};

static struct usb_class {
    struct kref kref;
    struct class *class;
} *usb_class;

static char *usb_devnode(struct device *dev, umode_t *mode)
{
    struct usb_class_driver *drv;

    drv = dev_get_drvdata(dev);
    if (!drv || !drv->devnode)
        return NULL;
    return drv->devnode(dev, mode);
}

static int init_usb_class(void)
{
    int result = 0;

    if (usb_class != NULL) {
        kref_get(&usb_class->kref);
        goto exit;
    }

    usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
    if (!usb_class) {
        result = -ENOMEM;
        goto exit;
    }

    kref_init(&usb_class->kref);
    usb_class->class = class_create(THIS_MODULE, "usbmisc");
    if (IS_ERR(usb_class->class)) {
        result = IS_ERR(usb_class->class);
        printk(KERN_ERR "class_create failed for usb devices\n");
        kfree(usb_class);
        usb_class = NULL;
        goto exit;
    }
    usb_class->class->devnode = usb_devnode;

exit:
    return result;
}

static void release_usb_class(struct kref *kref)
{
    /* Ok, we cheat as we know we only have one usb_class */
    class_destroy(usb_class->class);
    kfree(usb_class);
    usb_class = NULL;
}

static void destroy_usb_class(void)
{
    if (usb_class)
        kref_put(&usb_class->kref, release_usb_class);
}

int usb_major_init(void)
{
    int error;

    error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
    if (error)
        printk(KERN_ERR "Unable to get major %d for usb devices\n",
               USB_MAJOR);

    return error;
}

void usb_major_cleanup(void)
{
    unregister_chrdev(USB_MAJOR, "usb");
}

int usb_register_dev(struct usb_interface *intf,
             struct usb_class_driver *class_driver)
{
    int retval;
    int minor_base = class_driver->minor_base;
    int minor;
    char name[20];
    char *temp;

#ifdef CONFIG_USB_DYNAMIC_MINORS
    /* 
     * We don't care what the device tries to start at, we want to start
     * at zero to pack the devices into the smallest available space with
     * no holes in the minor range.
     */
    minor_base = 0;
#endif

    if (class_driver->fops == NULL)
        return -EINVAL;
    if (intf->minor >= 0)
        return -EADDRINUSE;

    retval = init_usb_class();
    if (retval)
        return retval;

    dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);

    down_write(&minor_rwsem);
    for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
        if (usb_minors[minor])
            continue;

        usb_minors[minor] = class_driver->fops;
        intf->minor = minor;
        break;
    }
    up_write(&minor_rwsem);
    if (intf->minor < 0)
        return -EXFULL;

    /* create a usb class device for this usb interface */
    snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
    temp = strrchr(name, '/');
    if (temp && (temp[1] != '\0'))
        ++temp;
    else
        temp = name;
    intf->usb_dev = device_create(usb_class->class, &intf->dev,
                      MKDEV(USB_MAJOR, minor), class_driver,
                      "%s", temp);
    if (IS_ERR(intf->usb_dev)) {
        down_write(&minor_rwsem);
        usb_minors[minor] = NULL;
        intf->minor = -1;
        up_write(&minor_rwsem);
        retval = PTR_ERR(intf->usb_dev);
    }
    return retval;
}
EXPORT_SYMBOL_GPL(usb_register_dev);

void usb_deregister_dev(struct usb_interface *intf,
            struct usb_class_driver *class_driver)
{
    if (intf->minor == -1)
        return;

    dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);

    down_write(&minor_rwsem);
    usb_minors[intf->minor] = NULL;
    up_write(&minor_rwsem);

    device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
    intf->usb_dev = NULL;
    intf->minor = -1;
    destroy_usb_class();
}
EXPORT_SYMBOL_GPL(usb_deregister_dev);