Linux内核USB驱动【转】

本文转载自：http://www.360doc.com/content/12/0321/14/8363527_196286673.shtml

注意,该文件是2.4的内核的驱动源文件,并不保证在2.6内核中可用.文件路径为kernel/driver/usb/usb_skelton.c

该文件是usb驱动的一个框架,很多usb的驱动都可以在这个文件的基础上进行修改得到.

下面就是该源文件,中文部分是我的注释,如有错误的地方,欢迎指出.

 /*
 * USB Skeleton driver - 0.6
 *
 * 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:
 *
 * 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 = ;
 #else
 static int debug;
 #endif
 //一个宏，用来调试时使用
 /* 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"
 //参量，可以在lsmod中更改
 /* Module paramaters */
 MODULE_PARM(debug, "i");
 MODULE_PARM_DESC(debug, "Debug enabled or not");
 //分别是厂商id和产品id
 /* Define these values to match your device */
 #define USB_SKEL_VENDOR_ID 0xfff0
 #define USB_SKEL_PRODUCT_ID 0xfff0
 //根据厂商和芯片id创建usb_device_id结构体
 /* 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 */
 };
 //将此结构体注册，提供给用户区空间的工具使用
 MODULE_DEVICE_TABLE (usb, skel_table);

 //主设备号的起始值
 /* Get a minor range for your devices from the usb maintainer */
 #define USB_SKEL_MINOR_BASE 200
 //设备数目
 /* we can have up to this number of device plugged in at once */
 #define MAX_DEVICES   16
 //一个自定义的结构体，用来存储驱动的相关信息
 //分别是设备，接口，设备句柄，主设备号的起始值，设备个数，中断端点数，批量输入端点数，批量输出端点数，
 //输入缓冲区首指针，大小，usb的端点地址
 //输出缓冲区首指针，大小，urb数组，usb的端点地址
 //工作队列，设备使用计数，信号量
 /* 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 */
 };
 //设备句柄
 /* the global usb devfs handle */
 extern devfs_handle_t usb_devfs_handle;
 //用来注册file_operations结构体的一些函数
 /* 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);
 //保存usb设备信息的结构体
 /* array of pointers to our devices that are currently connected */
 static struct usb_skel   *minor_table[MAX_DEVICES];
 //初始化信号量
 /* 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".
 */
 //字符串型设备所必须的结构体
 //依次为所有者，读函数，写函数，控制函数，打开函数，关闭函数
 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设备注册所必需的一个结构体，但只有name, probe, disconnect, idtable, owner五个是必须的
 /* usb specific object needed to register this driver with the usb subsystem */
 static struct usb_driver skel_driver = {
 owner:   THIS_MODULE,
 name:   "skeleton",
 probe:   skel_probe,
 disconnect: skel_disconnect,
 fops:   &skel_fops,
 minor:   USB_SKEL_MINOR_BASE,
 id_table: skel_table,
 };
 /**
 * usb_skel_debug_data
 */
 //用来debug的函数
 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 = ; i < size; ++i) {
    printk ("%.2x ", data[i]);
 }
 printk ("\n");
 }

 /**
 * skel_delete
 */
 //usb驱动程序卸载时将调用的函数
 static inline void skel_delete (struct usb_skel *dev)
 {
 minor_table[dev->minor] = NULL;
 //回收输入缓冲区内存
 if (dev->bulk_in_buffer != NULL)
    kfree (dev->bulk_in_buffer);
 //回收输出缓冲区内存
 if (dev->bulk_out_buffer != NULL)
    kfree (dev->bulk_out_buffer);
 //释放写入urb内存
 if (dev->write_urb != NULL)
    usb_free_urb (dev->write_urb);
 //释放整个结构体
 kfree (dev);
 }

 /**
 * skel_open
 */
 //打开设备函数，主要是用来初始化usb_skel结构体
 static int skel_open (struct inode *inode, struct file *file)
 {
 struct usb_skel *dev = NULL;
 int subminor;
 int retval = ;

 dbg(__FUNCTION__);
 //检测从设备号是否有问题
 subminor = MINOR (inode->i_rdev) - USB_SKEL_MINOR_BASE;
 if ((subminor < ) ||
      (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;
 //占有全局信号量，进入临界区域
 /* lock our minor table and get our local data for this minor */
 down (&minor_table_mutex);
 //得到当前设备的第subminor个usb_skel结构体
 dev = minor_table[subminor];
 if (dev == NULL) {
 //该设备不可用
    up (&minor_table_mutex);
    MOD_DEC_USE_COUNT;
    return -ENODEV;
 }
 //占有当前设备的信号量
 /* lock this device */
 down (&dev->sem);
 //释放全局信号量
 /* unlock the minor table */
 up (&minor_table_mutex);
 //打开设备计数加一
 /* increment our usage count for the driver */
 ++dev->open_count;
 //把当前设备的信心保存到设备驱动的结构体中
 /* save our object in the file's private structure */
 file->private_data = dev;
 //释放信号量
 /* unlock this device */
 up (&dev->sem);
 return retval;
 }

 /**
 * skel_release
 */
 //关闭函数
 static int skel_release (struct inode *inode, struct file *file)
 {
 struct usb_skel *dev;
 int retval = ;
 dev = (struct usb_skel *)file->private_data;
 if (dev == NULL) {
    dbg (__FUNCTION__ " - object is NULL");
    return -ENODEV;
 }
 dbg(__FUNCTION__ " - minor %d", dev->minor);
 //占有全局信号量
 /* lock our minor table */
 down (&minor_table_mutex);
 //占有局部信号量
 /* lock our device */
 down (&dev->sem);
 //设备引用计数小于0，说明目前没有打开设备
 if (dev->open_count <= ) {
    dbg (__FUNCTION__ " - device not opened");
    retval = -ENODEV;
    goto exit_not_opened;
 }
 //检测到设备已经拔出
 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 ;
 }
 //设备打开计数减一
 /* decrement our usage count for the device */
 --dev->open_count;
 if (dev->open_count <= ) {
 //没有任何人在使用该设备，则取消目前所有的数据传输
    /* shutdown any bulk writes that might be going on */
    usb_unlink_urb (dev->write_urb);
    dev->open_count = ;
 }
 //bookmark
 /* decrement our usage count for the module */
 MOD_DEC_USE_COUNT;
 //没有执行open就执行close
 exit_not_opened:
 up (&dev->sem);
 up (&minor_table_mutex);
 return retval;
 }

 /**
 * skel_read
 */
 //注意这里的数据传输并没有利用urb，而是用了一种简单的方式
 static ssize_t skel_read (struct file *file, char *buffer, size_t count, loff_t *ppos)
 {
 struct usb_skel *dev;
 int retval = ;
 dev = (struct usb_skel *)file->private_data;

 dbg(__FUNCTION__ " - minor %d, count = %d", dev->minor, count);
 //锁定信号量
 /* lock this object */
 down (&dev->sem);
 //该设备是否可用
 /* verify that the device wasn't unplugged */
 if (dev->udev == NULL) {
    up (&dev->sem);
    return -ENODEV;
 }
 //接收批量数据，同时指定了设备信息，批量输入的端点（通过usb_rcvbulkpipe构造），缓冲区地址和大小，所需要数据的大小，超时时间
 /* 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*);
 //数据正常接收
 //则把数据复制供给用户
 /* 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 = ;
 int retval = ;
 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;
 }
 //无效操作
 /* verify that we actually have some data to write */
 if (count == ) {
    dbg(__FUNCTION__ " - write request of 0 bytes");
    goto exit;
 }
 //设备正在忙碌
 /* see if we are already in the middle of a write */
 if (dev->write_urb->status == -EINPROGRESS) {
    dbg (__FUNCTION__ " - already writing");
    goto exit;
 }
 //计算写入的数据大小
 /* 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);
 //填充批量urb
 //目标urb，usb设备，目标端点（通过usb_sndbulkpipe创建），数据首地址，已写入数据的返回值，回调函数，提供给回调函数的数据
 /* 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);
 //正是发送urb
 /* 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;
 }
 //释放信号量
 exit:
 /* unlock the device */
 up (&dev->sem);
 return retval;
 }

 /**
 * skel_ioctl
 */
 //控制函数，并没有实质的功能
 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
 */
 //skel_write的回调函数
 static void skel_write_bulk_callback (struct urb *urb)
 {
 //用来获取skel_write失败时的设备信息
 struct usb_skel *dev = (struct usb_skel *)urb->context;
 //提供给debug函数的信息
 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.
 */
 //设备的试探函数
 static void * skel_probe(struct usb_device *udev, unsigned int ifnum, const struct usb_device_id *id)
 {
 //设备信息
 struct usb_skel *dev = NULL;
 //接口函数
 struct usb_interface *interface;
 //接口描述符
 struct usb_interface_descriptor *iface_desc;
 //端点结构体
 struct usb_endpoint_descriptor *endpoint;
 //从设备号
 int minor;
 //缓冲区大小
 int buffer_size;
 int i;
 char name[];
 //验证厂商和芯片id
 /* 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;
 }
 //临界区
 /* select a "subminor" number (part of a minor number) */
 down (&minor_table_mutex);
 //取得一个合适的从设备号
 for (minor = ; minor < MAX_DEVICES; ++minor) {
    if (minor_table[minor] == NULL)
     break;
 }
 //该从设备号不可用
 if (minor >= MAX_DEVICES) {
    info ("Too many devices plugged in, can not handle this device.");
    goto exit;
 }
 //申请内存
 /* 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;
 }
 minor_table[minor] = dev;
 //特定设备特定配置的特定接口
 interface = &udev->actconfig->interface[ifnum];
 //初始化从设备的信号量
 init_MUTEX (&dev->sem);
 //保存设备，配置以及接口方面的信息
 dev->udev = udev;
 dev->interface = interface;
 dev->minor = minor;
 /* set up the endpoint information */
 /* check out the endpoints */
 //搜索设备中可用的端点
 iface_desc = &interface->altsetting[];
 for (i = ; i < iface_desc->bNumEndpoints; ++i) {
    endpoint = &iface_desc->endpoint[i];
 //找到一个批量入端点，并配置相关信息：缓冲区大小，端点地址，缓冲区地址
 //由于采用简单方式，因此不需要在接收区使用urb
    if ((endpoint->bEndpointAddress & 0x80) &&
       ((endpoint->bmAttributes & ) == 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;
     }
    }
 //找到一个批量出端点，除前面的信息外还需要一个urb，并初始化该urb
    if (((endpoint->bEndpointAddress & 0x80) == 0x00) &&
       ((endpoint->bmAttributes & ) == 0x02)) {
     /* we found a bulk out endpoint */
     dev->write_urb = usb_alloc_urb();
     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;
     }
 //初始化该urbbookmark
     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);
 //初始化该设备文件，参数依次是：
 //设备句柄，驱动名称，名称长度（采用了默认值），主设备号，从设备号，权限（mode，gid，uid），file_operations结构体，额外的信息
 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);
 //提供给用户访问该文件系统时的信息
 /* 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;
 //出错处理
 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.
 */
 //设备移除时调用的函数
 static void skel_disconnect(struct usb_device *udev, void *ptr)
 {
 struct usb_skel *dev;
 int minor;
 //获取从设备信息
 dev = (struct usb_skel *)ptr;

 down (&minor_table_mutex);
 down (&dev->sem);

 minor = dev->minor;
 //设备文件注销
 /* remove our devfs node */
 devfs_unregister(dev->devfs);
 //当前设备没有被使用
 /* 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
 */
 //设备的初始化
 static int __init usb_skel_init(void)
 {
 int result;
 //设备注册
 /* register this driver with the USB subsystem */
 result = usb_register(&skel_driver);
 if (result < ) {
    err("usb_register failed for the "__FILE__" driver. Error number %d",
       result);
    return -;
 }
 info(DRIVER_DESC " " DRIVER_VERSION);
 return ;
 }

 /**
 * usb_skel_exit
 */
 //设备的注销，注意用的是usb_deregister而不是usb_unregister
 static void __exit usb_skel_exit(void)
 {
 /* deregister this driver with the USB subsystem */
 usb_deregister(&skel_driver);
 }
 //采用默认的函数进行驱动模块的初始化和注销
 module_init (usb_skel_init);
 module_exit (usb_skel_exit);
 MODULE_AUTHOR(DRIVER_AUTHOR);
 MODULE_DESCRIPTION(DRIVER_DESC);
 MODULE_LICENSE("GPL");