Libusb库的使用

Libusb库的使用

转自:http://blog.sina.com.cn/s/blog_4a5b632801009upv.html

 

使用libusb之前你的linux系统必须装有usb文件系统，这里还介绍了使用hiddev设备文件来访问设备，目的在于不仅可以比较出usb的易用性，还提供了一个转化成libusb驱动的案例。

3.1 find设备

任何驱动第一步首先是寻找到要操作的设备，我们先来看看HID驱动是怎样寻找到设备的。我们假设寻找设备的函数Device_Find(注：代码只是为了方便解说，不保证代码的健全)

int Device_Find()

{

 <wbr> </wbr><wbr> </wbr><wbr> char dir_str[100]; </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> char hiddev[100]; </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

DIR dir; <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

memset (dir_str, 0 , sizeof(dir_str));

memset (hiddev, 0 , sizeof(hiddev));

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

dir=opendir("/dev/usb/hid");

 <wbr> </wbr><wbr> </wbr><wbr> if(dir){</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> sprintf(dir_str,"/dev/usb/hid/");</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> closedir(dir);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }else{</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> sprintf(dir_str,"/dev/usb/");</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

for(i = 0; i < DEVICE_MINOR; i++) {

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> sprintf(hiddev, "%shiddev%d", dir_str,i);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> fd = open(hiddev, O_RDWR);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> if(fd > 0) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> ioctl(fd, HIDIOCGDEVINFO, &info);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> if(info.vendor== VENDOR_ID && info.product== PRODUCT_ID) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> device_num++; </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> close(fd);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> return device_num; </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

}

我们再来看libusb是如何来寻找和初始化设备

int Device_Find()

{

struct usb_bus  <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> *busses;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> int </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> device_num = 0;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> device_num = 0; </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> usb_init(); </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> usb_find_busses(); </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> usb_find_devices();</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

busses = usb_get_busses();

 <wbr> </wbr><wbr> </wbr><wbr> struct usb_bus </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> *bus;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> for (bus = busses; bus; bus = bus->next) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> struct usb_device *dev;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> for (dev = bus->devices; dev; dev = dev->next) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

if(dev->descriptor.idVendor==VENDOR_ID&& dev->descriptor.idProduct == PRODUCT_ID) {

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> device_num++; </wbr><wbr> </wbr><wbr></wbr>

} <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> } </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> return device_num; </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

}

注：在新版本的libusb中，usb_get_busses就可以不用了，这个函数是返回系统上的usb总线链表句柄

这里我们直接用usb_busses变量，这个变量在usb.h中被定义为外部变量

所以可以直接写成这样：

struct usb_bus  <wbr> </wbr><wbr> *bus;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> for (bus = usb_busses; bus; bus = bus->next) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> struct usb_device *dev;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> for (dev = bus->devices; dev; dev = dev->next) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> }</wbr>

}

3.2 打开设备

假设我们定义的打开设备的函数名是device_open,

int Device_Open()

{

 <wbr> </wbr><wbr> </wbr><wbr> int handle;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

handle = open(“hiddev0”, O_RDONLY);

}

int Device_Open()

{

struct usb_device* <wbr> </wbr><wbr> </wbr><wbr> udev;</wbr>

usb_dev_handle* <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> device_handle;</wbr>

device_handle = usb_open(udev);

}

3.3 读写设备和操作设备

假设我们的设备使用控制传输方式，至于批处理传输和中断传输限于篇幅这里不介绍

我们这里定义三个函数，Device_Write, Device_Read, Device_Report

Device_Report 功能发送接收函数

Device_Write 功能写数据

Device_Read <wbr> </wbr><wbr> 功能读数据</wbr>

Device_Write和Device_Read调用Device_Report发送写的信息和读的信息，开发者根据发送的命令协议来设计，我们这里只简单实现发送数据的函数。

假设我们要给设备发送72字节的数据，头8个字节是报告头，是我们定义的和设备相关的规则，后64位是数据。

HID驱动的实现(这里只是用代码来有助理解，代码是伪代码)

int Device_Report(int fd, unsigned char *buffer72)

{

int  <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> ret;</wbr>

int <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> index;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> unsigned char send_data[72];</wbr>

unsigned char recv_data[72];

 <wbr> </wbr><wbr> </wbr><wbr> struct hiddev_usage_ref uref;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> struct hiddev_report_info rinfo;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> ret = ioctl(fd, HIDIOCINITREPORT, 0);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> if( ret !=0) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> return NOT_OPENED_DEVICE;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> for(index = 0; index < 72; index++) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> uref.report_type = HID_REPORT_TYPE_FEATURE;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> uref.report_id = HID_REPORT_ID_FIRST;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> uref.usage_index = index;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> uref.field_index = 0;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> uref.value = send_data[index];</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> ioctl(fd, HIDIOCGUCODE, &uref);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> ret=ioctl(fd, HIDIOCSUSAGE, &uref);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> if(ret != 0 ){</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> return UNKNOWN_ERROR;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

}

rinfo.report_type = HID_REPORT_TYPE_FEATURE;

rinfo.report_id = HID_REPORT_ID_FIRST;

rinfo.num_fields = 1;

ret=ioctl(fd, HIDIOCSREPORT, &rinfo); <wbr> </wbr><wbr></wbr>

if(ret != 0) {

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> return WRITE_REPORT;</wbr>

}

ret = ioctl(fd, HIDIOCINITREPORT, 0);

for(index = 0; index < 72; index++) {

 <wbr> </wbr><wbr> </wbr><wbr> uref.report_type = HID_REPORT_TYPE_FEATURE;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> uref.report_id = HID_REPORT_ID_FIRST;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> uref.usage_index = index;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> uref.field_index = 0;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> ioctl(fd, HIDIOCGUCODE, &uref);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> ret = ioctl(fd, HIDIOCGUSAGE, &uref);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> if(ret != 0 ) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> return UNKNOWN_ERROR;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> recv_data[index] = uref.value;</wbr>

}

memcpy(buffer72, recv_data, 72);

return SUCCESS;

}

libusb驱动的实现

int Device_Report(int fd, unsigned char *buffer72)

{

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> usb_dev_handle* Device_handle;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> unsigned char </wbr><wbr> </wbr><wbr> send_data[72];</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> unsigned char </wbr><wbr> </wbr><wbr> recv_data[72];</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> int  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> send_len;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> int  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> recv_len;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> memset(send_data, 0 , sizeof(send_data));</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> memset(recv_data, 0 , sizeof(recv_data));</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> Device_handle = (usb_dev_handle*)(g_list[fd].device_handle);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> if (Device_handle == NULL) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> return NOT_OPENED_DEVICE;</wbr>

}

usb_claim_interface(Device_handle, 0);

send_len = usb_control_msg(Device_handle,

USB_ENDPOINT_OUT + USB_TYPE_CLASS + USB_RECIP_INTERFACE,

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> HID_REPORT_SET,</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> 0x300,</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> 0,</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> send_data, 72, USB_TIMEOUT);</wbr>

if (send_len < 0) {

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> return WRITE_REPORT;</wbr>

}

if (send_len != 72) {

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> return send_len;</wbr>

}

recv_len = usb_control_msg(Device_handle,

USB_ENDPOINT_IN + USB_TYPE_CLASS + USB_RECIP_INTERFACE,

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> HID_REPORT_GET,</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> 0x300,</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> 0,</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> recv_data, 72, USB_TIMEOUT);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> if (recv_len < 0) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> printf("failed to retrieve report from USB device!\n");</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> return READ_REPORT;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> if (recv_len != 72) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> return recv_len;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> usb_release_interface(RY2_handle, 0);</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> memcpy(buffer72, recv_data, 72);</wbr>

return SUCCESS;

}

3.4 关闭设备

假设我们定义的关闭设备的函数名是Device_Close()

int Device_Close()

{

 <wbr> </wbr><wbr> </wbr><wbr> int handle;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

handle = open(“hiddev0”, O_RDONLY);

close( handle );

}

int Device_Close()

{

struct usb_device* <wbr> </wbr><wbr> </wbr><wbr> udev;</wbr>

usb_dev_handle* <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> device_handle;</wbr>

device_handle = usb_open(udev);

usb_close(device_handle);

}

libusb的驱动框架

前面我们看了些主要的libusb函数的使用，这里我们把前面的内容归纳下：

一般的驱动应该都包含如下接口：

Device_Find();

Device_Open();

Device_Write();

Device_Read();

Device_Close();

具体代码如下：

#include <usb.h>

typedef struct

{

 <wbr> </wbr><wbr> </wbr><wbr> struct usb_device* </wbr><wbr> </wbr><wbr> </wbr><wbr> udev;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> usb_dev_handle* </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> device_handle;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

} device_descript;

#define USB_TIMEOUT <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> 10000</wbr>

#define VENDOR_ID <wbr> </wbr><wbr> </wbr><wbr> 0xffff </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

#define PRODUCT_ID <wbr> </wbr><wbr> 0xffff</wbr>

#define DEVICE_MINOR 16

int <wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> g_num;</wbr>

device_descript g_list[ DEVICE_MINOR ];

int Device_Find()

{

 <wbr> </wbr><wbr> </wbr><wbr> struct usb_bus </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> *bus;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> struct usb_device *dev;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> g_num = 0;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> usb_find_busses();</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> usb_find_devices();</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> for (bus = usb_busses; bus; bus = bus->next) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> for (dev = bus->devices; dev; dev = dev->next) {</wbr>

if(dev->descriptor.idVendor==VENDOR_ID&& dev->descriptor.idProduct == PRODUCT_ID) {

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> if (g_num < DEVICE_MINOR) {</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> g_list[g_num].udev = dev; </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> g_num ++;</wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> } </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> } </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr> }</wbr>

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> return g_num;</wbr>

}

int Device_Open()

{

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

 <wbr> </wbr><wbr> </wbr><wbr> if(g_list[g_num].udev != NULL) {
 </wbr><wbr> </wbr><wbr> </wbr><wbr>  </wbr><wbr> </wbr><wbr> </wbr><wbr> g_list[g_num].device_handle = usb_open(g_list[g_num].udev);</wbr>

}

}

int DeviceWite(int handle)

{

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

}

int DeviceOpen(int handle)

{

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

}

void Device_close(int handle)

{

 <wbr> </wbr><wbr> </wbr><wbr></wbr>

}

小结

 <wbr> </wbr><wbr> 到此，使用libusb进行驱动开发介绍完了，通过对库所提供的API的使用可以体会到libusb的易用性。
</wbr>