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f7294055a7
This weekend I was hacking around with a trivial USB driver for talking to the boot load firmware of a USB Bit Whacker. It's running the MicroChip Pic18 boot loader firmware and I'm putting together a flash program for writing new FW to the thing. Anyway in my use of the usb-skeleton.c as my starting point I discovered my test program was getting hung up after attempting to write a buffer. The application and driver where hung in a way that required me to reboot to get it to clean up so I could try again. It turned out the code path through skel_open can grap the driver's io_mutex lock and forget to release it. The following patch fixes the problem for me. Signed-off-by: Mark Gross <mgross@linux.intel.com> Cc: Oliver Neukum <oliver@neukum.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
526 lines
13 KiB
C
526 lines
13 KiB
C
/*
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* USB Skeleton driver - 2.2
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*
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* Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2.
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*
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* This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
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* but has been rewritten to be easier to read and use.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/kref.h>
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#include <asm/uaccess.h>
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#include <linux/usb.h>
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#include <linux/mutex.h>
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/* Define these values to match your devices */
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#define USB_SKEL_VENDOR_ID 0xfff0
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#define USB_SKEL_PRODUCT_ID 0xfff0
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/* table of devices that work with this driver */
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static struct usb_device_id skel_table [] = {
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{ USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
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{ } /* Terminating entry */
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};
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MODULE_DEVICE_TABLE(usb, skel_table);
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/* Get a minor range for your devices from the usb maintainer */
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#define USB_SKEL_MINOR_BASE 192
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/* our private defines. if this grows any larger, use your own .h file */
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#define MAX_TRANSFER (PAGE_SIZE - 512)
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/* MAX_TRANSFER is chosen so that the VM is not stressed by
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allocations > PAGE_SIZE and the number of packets in a page
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is an integer 512 is the largest possible packet on EHCI */
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#define WRITES_IN_FLIGHT 8
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/* arbitrarily chosen */
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/* Structure to hold all of our device specific stuff */
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struct usb_skel {
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struct usb_device *udev; /* the usb device for this device */
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struct usb_interface *interface; /* the interface for this device */
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struct semaphore limit_sem; /* limiting the number of writes in progress */
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struct usb_anchor submitted; /* in case we need to retract our submissions */
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unsigned char *bulk_in_buffer; /* the buffer to receive data */
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size_t bulk_in_size; /* the size of the receive buffer */
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__u8 bulk_in_endpointAddr; /* the address of the bulk in endpoint */
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__u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */
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int errors; /* the last request tanked */
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int open_count; /* count the number of openers */
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spinlock_t err_lock; /* lock for errors */
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struct kref kref;
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struct mutex io_mutex; /* synchronize I/O with disconnect */
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};
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#define to_skel_dev(d) container_of(d, struct usb_skel, kref)
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static struct usb_driver skel_driver;
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static void skel_draw_down(struct usb_skel *dev);
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static void skel_delete(struct kref *kref)
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{
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struct usb_skel *dev = to_skel_dev(kref);
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usb_put_dev(dev->udev);
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kfree(dev->bulk_in_buffer);
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kfree(dev);
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}
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static int skel_open(struct inode *inode, struct file *file)
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{
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struct usb_skel *dev;
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struct usb_interface *interface;
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int subminor;
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int retval = 0;
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subminor = iminor(inode);
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interface = usb_find_interface(&skel_driver, subminor);
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if (!interface) {
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err ("%s - error, can't find device for minor %d",
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__FUNCTION__, subminor);
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retval = -ENODEV;
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goto exit;
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}
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dev = usb_get_intfdata(interface);
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if (!dev) {
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retval = -ENODEV;
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goto exit;
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}
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/* increment our usage count for the device */
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kref_get(&dev->kref);
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/* lock the device to allow correctly handling errors
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* in resumption */
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mutex_lock(&dev->io_mutex);
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if (!dev->open_count++) {
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retval = usb_autopm_get_interface(interface);
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if (retval) {
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dev->open_count--;
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mutex_unlock(&dev->io_mutex);
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kref_put(&dev->kref, skel_delete);
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goto exit;
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}
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} /* else { //uncomment this block if you want exclusive open
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retval = -EBUSY;
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dev->open_count--;
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mutex_unlock(&dev->io_mutex);
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kref_put(&dev->kref, skel_delete);
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goto exit;
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} */
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/* prevent the device from being autosuspended */
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/* save our object in the file's private structure */
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file->private_data = dev;
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mutex_unlock(&dev->io_mutex);
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exit:
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return retval;
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}
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static int skel_release(struct inode *inode, struct file *file)
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{
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struct usb_skel *dev;
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dev = (struct usb_skel *)file->private_data;
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if (dev == NULL)
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return -ENODEV;
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/* allow the device to be autosuspended */
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mutex_lock(&dev->io_mutex);
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if (!--dev->open_count && dev->interface)
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usb_autopm_put_interface(dev->interface);
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mutex_unlock(&dev->io_mutex);
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/* decrement the count on our device */
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kref_put(&dev->kref, skel_delete);
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return 0;
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}
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static int skel_flush(struct file *file, fl_owner_t id)
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{
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struct usb_skel *dev;
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int res;
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dev = (struct usb_skel *)file->private_data;
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if (dev == NULL)
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return -ENODEV;
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/* wait for io to stop */
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mutex_lock(&dev->io_mutex);
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skel_draw_down(dev);
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/* read out errors, leave subsequent opens a clean slate */
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spin_lock_irq(&dev->err_lock);
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res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
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dev->errors = 0;
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spin_unlock_irq(&dev->err_lock);
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mutex_unlock(&dev->io_mutex);
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return res;
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}
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static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
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{
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struct usb_skel *dev;
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int retval;
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int bytes_read;
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dev = (struct usb_skel *)file->private_data;
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mutex_lock(&dev->io_mutex);
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if (!dev->interface) { /* disconnect() was called */
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retval = -ENODEV;
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goto exit;
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}
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/* do a blocking bulk read to get data from the device */
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retval = usb_bulk_msg(dev->udev,
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usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),
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dev->bulk_in_buffer,
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min(dev->bulk_in_size, count),
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&bytes_read, 10000);
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/* if the read was successful, copy the data to userspace */
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if (!retval) {
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if (copy_to_user(buffer, dev->bulk_in_buffer, bytes_read))
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retval = -EFAULT;
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else
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retval = bytes_read;
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}
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exit:
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mutex_unlock(&dev->io_mutex);
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return retval;
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}
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static void skel_write_bulk_callback(struct urb *urb)
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{
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struct usb_skel *dev;
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dev = (struct usb_skel *)urb->context;
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/* sync/async unlink faults aren't errors */
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if (urb->status) {
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if(!(urb->status == -ENOENT ||
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urb->status == -ECONNRESET ||
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urb->status == -ESHUTDOWN))
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err("%s - nonzero write bulk status received: %d",
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__FUNCTION__, urb->status);
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spin_lock(&dev->err_lock);
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dev->errors = urb->status;
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spin_unlock(&dev->err_lock);
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}
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/* free up our allocated buffer */
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usb_buffer_free(urb->dev, urb->transfer_buffer_length,
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urb->transfer_buffer, urb->transfer_dma);
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up(&dev->limit_sem);
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}
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static ssize_t skel_write(struct file *file, const char *user_buffer, size_t count, loff_t *ppos)
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{
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struct usb_skel *dev;
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int retval = 0;
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struct urb *urb = NULL;
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char *buf = NULL;
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size_t writesize = min(count, (size_t)MAX_TRANSFER);
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dev = (struct usb_skel *)file->private_data;
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/* verify that we actually have some data to write */
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if (count == 0)
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goto exit;
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/* limit the number of URBs in flight to stop a user from using up all RAM */
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if (down_interruptible(&dev->limit_sem)) {
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retval = -ERESTARTSYS;
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goto exit;
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}
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spin_lock_irq(&dev->err_lock);
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if ((retval = dev->errors) < 0) {
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/* any error is reported once */
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dev->errors = 0;
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/* to preserve notifications about reset */
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retval = (retval == -EPIPE) ? retval : -EIO;
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}
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spin_unlock_irq(&dev->err_lock);
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if (retval < 0)
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goto error;
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/* create a urb, and a buffer for it, and copy the data to the urb */
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urb = usb_alloc_urb(0, GFP_KERNEL);
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if (!urb) {
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retval = -ENOMEM;
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goto error;
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}
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buf = usb_buffer_alloc(dev->udev, writesize, GFP_KERNEL, &urb->transfer_dma);
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if (!buf) {
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retval = -ENOMEM;
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goto error;
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}
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if (copy_from_user(buf, user_buffer, writesize)) {
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retval = -EFAULT;
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goto error;
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}
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/* this lock makes sure we don't submit URBs to gone devices */
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mutex_lock(&dev->io_mutex);
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if (!dev->interface) { /* disconnect() was called */
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mutex_unlock(&dev->io_mutex);
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retval = -ENODEV;
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goto error;
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}
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/* initialize the urb properly */
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usb_fill_bulk_urb(urb, dev->udev,
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usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
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buf, writesize, skel_write_bulk_callback, dev);
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urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
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usb_anchor_urb(urb, &dev->submitted);
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/* send the data out the bulk port */
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retval = usb_submit_urb(urb, GFP_KERNEL);
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mutex_unlock(&dev->io_mutex);
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if (retval) {
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err("%s - failed submitting write urb, error %d", __FUNCTION__, retval);
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goto error_unanchor;
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}
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/* release our reference to this urb, the USB core will eventually free it entirely */
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usb_free_urb(urb);
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return writesize;
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error_unanchor:
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usb_unanchor_urb(urb);
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error:
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if (urb) {
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usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma);
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usb_free_urb(urb);
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}
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up(&dev->limit_sem);
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exit:
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return retval;
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}
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static const struct file_operations skel_fops = {
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.owner = THIS_MODULE,
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.read = skel_read,
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.write = skel_write,
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.open = skel_open,
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.release = skel_release,
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.flush = skel_flush,
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};
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/*
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* usb class driver info in order to get a minor number from the usb core,
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* and to have the device registered with the driver core
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*/
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static struct usb_class_driver skel_class = {
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.name = "skel%d",
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.fops = &skel_fops,
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.minor_base = USB_SKEL_MINOR_BASE,
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};
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static int skel_probe(struct usb_interface *interface, const struct usb_device_id *id)
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{
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struct usb_skel *dev;
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struct usb_host_interface *iface_desc;
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struct usb_endpoint_descriptor *endpoint;
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size_t buffer_size;
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int i;
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int retval = -ENOMEM;
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/* allocate memory for our device state and initialize it */
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dev = kzalloc(sizeof(*dev), GFP_KERNEL);
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if (!dev) {
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err("Out of memory");
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goto error;
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}
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kref_init(&dev->kref);
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sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
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mutex_init(&dev->io_mutex);
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spin_lock_init(&dev->err_lock);
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init_usb_anchor(&dev->submitted);
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dev->udev = usb_get_dev(interface_to_usbdev(interface));
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dev->interface = interface;
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/* set up the endpoint information */
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/* use only the first bulk-in and bulk-out endpoints */
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iface_desc = interface->cur_altsetting;
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for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
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endpoint = &iface_desc->endpoint[i].desc;
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if (!dev->bulk_in_endpointAddr &&
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usb_endpoint_is_bulk_in(endpoint)) {
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/* we found a bulk in endpoint */
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buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
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dev->bulk_in_size = buffer_size;
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dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
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dev->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);
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if (!dev->bulk_in_buffer) {
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err("Could not allocate bulk_in_buffer");
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goto error;
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}
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}
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if (!dev->bulk_out_endpointAddr &&
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usb_endpoint_is_bulk_out(endpoint)) {
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/* we found a bulk out endpoint */
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dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
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}
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}
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if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
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err("Could not find both bulk-in and bulk-out endpoints");
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goto error;
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}
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/* save our data pointer in this interface device */
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usb_set_intfdata(interface, dev);
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/* we can register the device now, as it is ready */
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retval = usb_register_dev(interface, &skel_class);
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if (retval) {
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/* something prevented us from registering this driver */
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err("Not able to get a minor for this device.");
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usb_set_intfdata(interface, NULL);
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goto error;
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}
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/* let the user know what node this device is now attached to */
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info("USB Skeleton device now attached to USBSkel-%d", interface->minor);
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return 0;
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error:
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if (dev)
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/* this frees allocated memory */
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kref_put(&dev->kref, skel_delete);
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return retval;
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}
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static void skel_disconnect(struct usb_interface *interface)
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{
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struct usb_skel *dev;
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int minor = interface->minor;
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dev = usb_get_intfdata(interface);
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usb_set_intfdata(interface, NULL);
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/* give back our minor */
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usb_deregister_dev(interface, &skel_class);
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/* prevent more I/O from starting */
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mutex_lock(&dev->io_mutex);
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dev->interface = NULL;
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mutex_unlock(&dev->io_mutex);
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usb_kill_anchored_urbs(&dev->submitted);
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/* decrement our usage count */
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kref_put(&dev->kref, skel_delete);
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info("USB Skeleton #%d now disconnected", minor);
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}
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static void skel_draw_down(struct usb_skel *dev)
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{
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int time;
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time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
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if (!time)
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usb_kill_anchored_urbs(&dev->submitted);
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}
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static int skel_suspend(struct usb_interface *intf, pm_message_t message)
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{
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struct usb_skel *dev = usb_get_intfdata(intf);
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if (!dev)
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return 0;
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skel_draw_down(dev);
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return 0;
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}
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static int skel_resume (struct usb_interface *intf)
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{
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return 0;
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}
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static int skel_pre_reset(struct usb_interface *intf)
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{
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struct usb_skel *dev = usb_get_intfdata(intf);
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mutex_lock(&dev->io_mutex);
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skel_draw_down(dev);
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return 0;
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}
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static int skel_post_reset(struct usb_interface *intf)
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{
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struct usb_skel *dev = usb_get_intfdata(intf);
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/* we are sure no URBs are active - no locking needed */
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dev->errors = -EPIPE;
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mutex_unlock(&dev->io_mutex);
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return 0;
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}
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static struct usb_driver skel_driver = {
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.name = "skeleton",
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.probe = skel_probe,
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.disconnect = skel_disconnect,
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.suspend = skel_suspend,
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.resume = skel_resume,
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.pre_reset = skel_pre_reset,
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.post_reset = skel_post_reset,
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.id_table = skel_table,
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.supports_autosuspend = 1,
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};
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static int __init usb_skel_init(void)
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{
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int result;
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/* register this driver with the USB subsystem */
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result = usb_register(&skel_driver);
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if (result)
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err("usb_register failed. Error number %d", result);
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return result;
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}
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static void __exit usb_skel_exit(void)
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{
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/* deregister this driver with the USB subsystem */
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usb_deregister(&skel_driver);
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}
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module_init(usb_skel_init);
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module_exit(usb_skel_exit);
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MODULE_LICENSE("GPL");
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