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 ([e-mail])
*
* 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 = 1;
#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, [e-mail]"
#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 = 0; 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 = 0;

dbg(__FUNCTION__);
//检测从设备号是否有问题
subminor = MINOR (inode->i_rdev) - USB_SKEL_MINOR_BASE;
if ((subminor < 0) ||
     (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 = 0;
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 <= 0) {
   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 0;
}
//设备打开计数减一
/* decrement our usage count for the device */
--dev->open_count;
if (dev->open_count <= 0) {
//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 = 0;
}
//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 = 0;
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*10);
//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 = 0;
int retval = 0;
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 == 0) {
   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[10];
//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 = 0; 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[0];
for (i = 0; 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 & 3) == 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 & 3) == 0x02)) {
    /* we found a bulk out endpoint */
    dev->write_urb = usb_alloc_urb(0);
    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 < 0) {
   err("usb_register failed for the "__FILE__" driver. Error number %d",
      result);
   return -1;
}
info(DRIVER_DESC " " DRIVER_VERSION);
return 0;
}

/**
* 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");