Linux usb驱动程序全注释 .

http://blog.csdn.net/gotosola/article/details/7473730

/*

 * USB Skeleton driver - 2.0

 */

#include <linux/config.h>

#include <linux/kernel.h>

#include <linux/errno.h>

#include <linux/init.h>

#include <linux/slab.h>

#include <linux/module.h>

#include <linux/kref.h>

#include <linux/smp_lock.h>

#include <linux/usb.h>

#include <asm/uaccess.h>

/* Define these values to match your devices */

#define USB_SKEL_VENDOR_ID 0xfff0//定义厂商ID

#define USB_SKEL_PRODUCT_ID 0xfff0//定义产品ID

/* 描述驱动支持的USB设备结构 */

static struct usb_device_id skel_table [] = {

 { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },

 { }     /* Terminating entry */

};

MODULE_DEVICE_TABLE (usb, skel_table);

/* Get a minor range for your devices from the usb maintainer */

#define USB_SKEL_MINOR_BASE 192

/* 定义一个结构包含所有我们所需要的设备成员 */

struct usb_skel {

 struct usb_device * udev;   /* the usb device for this device */

 struct usb_interface * interface;  /* the interface for this device */

 unsigned char *  bulk_in_buffer;  /* the buffer to receive data */

 size_t   bulk_in_size;  /* the size of the receive buffer */

 __u8   bulk_in_endpointAddr; /* the address of the bulk in endpoint */

 __u8   bulk_out_endpointAddr; /* the address of the bulk out endpoint */

 struct kref  kref;/*内核引用计数*/

};

#define to_skel_dev(d) container_of(d, struct usb_skel, kref)

static struct usb_driver skel_driver;//定义一个usb设备驱动

static void skel_delete(struct kref *kref)

{ 

 struct usb_skel *dev = to_skel_dev(kref);

 usb_put_dev(dev->udev);

 kfree (dev->bulk_in_buffer);

 kfree (dev);

}

 

/*设备打开函数*/

static int skel_open(struct inode *inode, struct file *file)

{

 struct usb_skel *dev;//定义一个本地结构体引用

 struct usb_interface *interface;//定义一个usb设备主结构体引用

 int subminor;

 int retval = 0;

 /*在inode中的i_rdev成员中存储着设备文件的设备号，通过iminor可以从inode中获取

 设备文件的次设备号*/

 subminor = iminor(inode);

 

 /*遍历驱动获取次设备号匹配的usb主设备结构体*/

 interface = usb_find_interface(&skel_driver, subminor);

 if (!interface) {

  err ("%s - error, can't find device for minor %d",

       __FUNCTION__, subminor);

  retval = -ENODEV;

  goto exit;

 }

 /*从interface中获取数据保存到dev中*/

 dev = usb_get_intfdata(interface);

 if (!dev) {

  retval = -ENODEV;

  goto exit;

 }

 

 /* increment our usage count for the device */

 /*增加设备的内核使用计数*/

 kref_get(&dev->kref);

 /* save our object in the file's private structure */

 /*将获取的本地设备保存到文件私有数据当中*/

 file->private_data = dev;

exit:

 return retval;

}

static int skel_release(struct inode *inode, struct file *file)

{

 struct usb_skel *dev;

 /*获取本地usb设备*/

 dev = (struct usb_skel *)file->private_data;

 if (dev == NULL)

  return -ENODEV;

 /* decrement the count on our device */

 /*减少usb设备的内核使用计数*/

 kref_put(&dev->kref, skel_delete);

 return 0;

}

/*设备读函数*/

static ssize_t skel_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos)

{

/*这里在读函数中我们使用无urb的方法实现数据的传输*/

 struct usb_skel *dev;

 int retval = 0;

 //获取本地设备结构体

 dev = (struct usb_skel *)file->private_data;

 

 /* do a blocking bulk read to get data from the device */

 /*从usb设备中获取数据保存到dev的bulk_in_buffer，

 当然此函数也可以发送数据到usb设备当中，主要取决于第二参数是in端点还是out端点*/

 retval = usb_bulk_msg(dev->udev,

         usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),

         dev->bulk_in_buffer,

         min(dev->bulk_in_size, count),

         &count, HZ*10);

 /* if the read was successful, copy the data to userspace */

 if (!retval) {

  //将接收到的数据拷贝到用户空间

  if (copy_to_user(buffer, dev->bulk_in_buffer, count))

   retval = -EFAULT;

  else

   retval = count;

 }

 return retval;

}

 

/*urb写入完成回调函数*/

static void skel_write_bulk_callback(struct urb *urb, struct pt_regs *regs)

{

 /* sync/async unlink faults aren't errors */

 /*通过检查urb的状态来确定urb是否成功完成*/

 if (urb->status &&

     !(urb->status == -ENOENT ||

       urb->status == -ECONNRESET ||

       urb->status == -ESHUTDOWN)) {

  dbg("%s - nonzero write bulk status received: %d",

      __FUNCTION__, urb->status);

 }

 /* free up our allocated buffer */

 /*释放安排给这个urb传送的已分配的缓冲*/

 usb_buffer_free(urb->dev, urb->transfer_buffer_length,

   urb->transfer_buffer, urb->transfer_dma);

}

 

/*字符设备写函数*/

static ssize_t skel_write(struct file *file, const char __user *user_buffer, size_t count, loff_t *ppos)

{

 struct usb_skel *dev;

 int retval = 0;

 struct urb *urb = NULL;

 char *buf = NULL;

 /*获取usb本地设备结构*/

 dev = (struct usb_skel *)file->private_data;

 /* verify that we actually have some data to write */

 if (count == 0)

  goto exit;

 /* create a urb, and a buffer for it, and copy the data to the urb */

 /*创建一个urb*/

 urb = usb_alloc_urb(0, GFP_KERNEL);

 if (!urb) {

  retval = -ENOMEM;

  goto error;

 }

 /*分配一个dma缓冲buf*/

 buf = usb_buffer_alloc(dev->udev, count, GFP_KERNEL, &urb->transfer_dma);

 if (!buf) {

  retval = -ENOMEM;

  goto error;

 }

 /*将用户空间写入的数据拷贝到缓冲区buf中*/

 if (copy_from_user(buf, user_buffer, count)) {

  retval = -EFAULT;

  goto error;

 }

 /* initialize the urb properly */

 /*在urb被提交之前需要被初始化*/

 /*在这里传入写入完成回调函数指针skel_write_bulk_callback*/

 usb_fill_bulk_urb(urb, dev->udev,

     usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),

     buf, count, skel_write_bulk_callback, dev);

 urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

 

 

 /* send the data out the bulk port */

 /*当urb的分配，数据拷贝，初始完成之后，就可以将urb提交给设备*/

 retval = usb_submit_urb(urb, GFP_KERNEL);

 if (retval) {

  err("%s - failed submitting write urb, error %d", __FUNCTION__, retval);

  goto error;

 }

 /* release our reference to this urb, the USB core will eventually free it entirely */

 usb_free_urb(urb);

exit:

 return count;

error:

 usb_buffer_free(dev->udev, count, buf, urb->transfer_dma);

 usb_free_urb(urb);

 kfree(buf);

 return retval;

}

static struct file_operations skel_fops = {

 .owner = THIS_MODULE,

 .read =  skel_read,

 .write = skel_write,

 .open =  skel_open,

 .release = skel_release,

};

/*

 * usb class driver info in order to get a minor number from the usb core,

 * and to have the device registered with devfs and the driver core

 */

 /**usb 类驱动 信息 使我们 能 从usb core  usb核  得到一个次 设备

 从而可以 使 设备被 注册 到 驱动内核中**/

static struct usb_class_driver skel_class = {

 .name = "usb/skel%d",//设备结构的名称

 .fops = &skel_fops,

 .mode = S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH,

 .minor_base = USB_SKEL_MINOR_BASE,

};

 

 

/*探测函数的写法*/

static int skel_probe(struct usb_interface *interface, const struct usb_device_id *id)

{

 struct usb_skel *dev = NULL;

 struct usb_host_interface *iface_desc;

 struct usb_endpoint_descriptor *endpoint;

 size_t buffer_size;

 int i;

 int retval = -ENOMEM;

 /* allocate memory for our device state and initialize it */

 /*为我们定义的设备结构分配内存*/

 dev = kmalloc(sizeof(struct usb_skel), GFP_KERNEL);

 if (dev == NULL) {

  err("Out of memory");

  goto error;

 }

 memset(dev, 0x00, sizeof (*dev));

 kref_init(&dev->kref);//初始化内核引用计数

 /*获取usb设备结构体*/

 dev->udev = usb_get_dev(interface_to_usbdev(interface));

 /*设置usb主设备结构体对象*/

 dev->interface = interface;

 /* set up the endpoint information */

 /* use only the first bulk-in and bulk-out endpoints */

 /*设置端点信息

 */

 iface_desc = interface->cur_altsetting;

 for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {

  endpoint = &iface_desc->endpoint[i].desc;

  /*判断此端点方向是否为IN

  判断此端点类型是否为块bulk*/

  if (!dev->bulk_in_endpointAddr &&

      (endpoint->bEndpointAddress & USB_DIR_IN) &&

      ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)

     == USB_ENDPOINT_XFER_BULK)) {

   /* we found a bulk in endpoint */

   /*如果满足条件，将端点信息保存到本地设备结构体中*/

   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("Could not allocate bulk_in_buffer");

    goto error;

   }

  }

  if (!dev->bulk_out_endpointAddr &&

      !(endpoint->bEndpointAddress & USB_DIR_IN) &&

      ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)

     == USB_ENDPOINT_XFER_BULK)) {

   /* we found a bulk out endpoint */

   /*如果发现一个OUT块端点，将端点地址付给本地设备结构体中的相关成员*/

   dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;

  }

 }

 if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {

  err("Could not find both bulk-in and bulk-out endpoints");

  goto error;

 }

 /* save our data pointer in this interface device */

 /*保存我们的设备数据指针到主USB设备*/

 usb_set_intfdata(interface, dev);

 /* we can register the device now, as it is ready */

 /*现在设备已经准备好了，我们可以注册它了*/

 retval = usb_register_dev(interface, &skel_class);

 if (retval) {

  /* something prevented us from registering this driver */

  err("Not able to get a minor for this device.");

  usb_set_intfdata(interface, NULL);

  goto error;

 }

 /* let the user know what node this device is now attached to */

 info("USB Skeleton device now attached to USBSkel-%d", interface->minor);

 return 0;

error:

 if (dev)

  kref_put(&dev->kref, skel_delete);

 return retval;

}

 

/*去连接函数*/

static void skel_disconnect(struct usb_interface *interface)

{

 struct usb_skel *dev;

 int minor = interface->minor;

 /* prevent skel_open() from racing skel_disconnect() */

 /*获取bigkernel锁，阻止open()调用*/

 lock_kernel();

 /*从usb主设备结构中获取信息到usb设备结构当中*/

 dev = usb_get_intfdata(interface);

 /*设置usb主设备为NULL*/

 usb_set_intfdata(interface, NULL);

 /* give back our minor */

 /*注销usb设备*/

 usb_deregister_dev(interface, &skel_class);

 /*解除锁*/

 unlock_kernel();

 /* decrement our usage count */

 /*减少usb使用计数，释放usb设备缓冲区*/

 kref_put(&dev->kref, skel_delete);

 /*打印相关信息*/

 info("USB Skeleton #%d now disconnected", minor);

}

 

//定义并初始化usb驱动，只需要初始化这五个成员就可以了

static struct usb_driver skel_driver = {

 .owner = THIS_MODULE,//指向驱动

 .name = "skeleton",//驱动名字

 .id_table = skel_table,//可匹配的USB类型列表

 .probe = skel_probe,//指向USB驱动程序中探测函数的指针

 .disconnect = skel_disconnect,//指向USB驱动中去连接函数的指针

};

 

/*usb模块初始化函数*/

static int __init usb_skel_init(void)

{

 int result;

 /* register this driver with the USB subsystem */

 /*注册驱动*/

 result = usb_register(&skel_driver);

 if (result)

  err("usb_register failed. Error number %d", result);

 return result;

}

 

/*usb模块卸载函数*/

static void __exit usb_skel_exit(void)

{

 /* deregister this driver with the USB subsystem */

 /*注销usb驱动*/

 usb_deregister(&skel_driver);

}

module_init (usb_skel_init);

module_exit (usb_skel_exit);

MODULE_LICENSE("GPL");