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![David Howells](/assets/img/avatar_default.png)
Maintain a per-CPU global "struct pt_regs *" variable which can be used instead of passing regs around manually through all ~1800 interrupt handlers in the Linux kernel. The regs pointer is used in few places, but it potentially costs both stack space and code to pass it around. On the FRV arch, removing the regs parameter from all the genirq function results in a 20% speed up of the IRQ exit path (ie: from leaving timer_interrupt() to leaving do_IRQ()). Where appropriate, an arch may override the generic storage facility and do something different with the variable. On FRV, for instance, the address is maintained in GR28 at all times inside the kernel as part of general exception handling. Having looked over the code, it appears that the parameter may be handed down through up to twenty or so layers of functions. Consider a USB character device attached to a USB hub, attached to a USB controller that posts its interrupts through a cascaded auxiliary interrupt controller. A character device driver may want to pass regs to the sysrq handler through the input layer which adds another few layers of parameter passing. I've build this code with allyesconfig for x86_64 and i386. I've runtested the main part of the code on FRV and i386, though I can't test most of the drivers. I've also done partial conversion for powerpc and MIPS - these at least compile with minimal configurations. This will affect all archs. Mostly the changes should be relatively easy. Take do_IRQ(), store the regs pointer at the beginning, saving the old one: struct pt_regs *old_regs = set_irq_regs(regs); And put the old one back at the end: set_irq_regs(old_regs); Don't pass regs through to generic_handle_irq() or __do_IRQ(). In timer_interrupt(), this sort of change will be necessary: - update_process_times(user_mode(regs)); - profile_tick(CPU_PROFILING, regs); + update_process_times(user_mode(get_irq_regs())); + profile_tick(CPU_PROFILING); I'd like to move update_process_times()'s use of get_irq_regs() into itself, except that i386, alone of the archs, uses something other than user_mode(). Some notes on the interrupt handling in the drivers: (*) input_dev() is now gone entirely. The regs pointer is no longer stored in the input_dev struct. (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking. It does something different depending on whether it's been supplied with a regs pointer or not. (*) Various IRQ handler function pointers have been moved to type irq_handler_t. Signed-Off-By: David Howells <dhowells@redhat.com> (cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
404 lines
10 KiB
C
404 lines
10 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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#define WRITES_IN_FLIGHT 8
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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 *dev; /* 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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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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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_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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/* prevent the device from being autosuspended */
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retval = usb_autopm_get_interface(interface);
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if (retval)
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goto exit;
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/* increment our usage count for the device */
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kref_get(&dev->kref);
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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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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->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 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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!(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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}
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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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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 error;
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}
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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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/* 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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/* send the data out the bulk port */
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retval = usb_submit_urb(urb, GFP_KERNEL);
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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;
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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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mutex_unlock(&dev->io_mutex);
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return writesize;
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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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mutex_unlock(&dev->io_mutex);
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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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};
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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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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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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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/* prevent skel_open() from racing skel_disconnect() */
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lock_kernel();
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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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unlock_kernel();
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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 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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.id_table = skel_table,
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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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