Question

我有一些代码，可以找到所有已连接的USB设备，其VendorID和ProductID。

我需要一个程序，该程序可以通过显示器或触摸板的VID和PID查找连接的设备。我发现libusb_class_code带有视频类，但没有找到任何返回libusb_class_code的函数。

libusb_context *context = nullptr;
libusb_device **list = nullptr;

libusb_init(&context);
int count = libusb_get_device_list(context, &list);

for (size_t idx = 0; idx < count; ++idx)
{
    libusb_device *device = list[idx];
    libusb_device_descriptor desc = { 0 };

    libusb_get_device_descriptor(device, &desc);

    cout << "idVendor  " << desc.idVendor << "\t";
    cout << "idProduct " << desc.idProduct << endl;

}

Answer 1

如果要通过VID和PID访问给定设备，则有一个专用功能libusb_open_device_with_vid_pid。

这是一个简单的示例，显示了如何打开设备，处理接口，读取数据然后将其关闭。

libusb_context       *context    = NULL   ;
libusb_device_handle *dev_handle = NULL   ;
libusb_device        **devs               ;
int                  rc          = 0      ;
ssize_t              count                ; //holding number of devices in list

//----------------------------------------------------------------------------
// Initialize the library
//----------------------------------------------------------------------------
rc = libusb_init(&context);
assert(rc == 0);

//----------------------------------------------------------------------------
// open usb device by vendor ID and Product ID
//----------------------------------------------------------------------------
dev_handle = libusb_open_device_with_vid_pid(context,VENDOR_ID,PRODUCT_ID);
assert(dev_handle == NULL);

//----------------------------------------------------------------------------
// Check that the kernel is attached
//----------------------------------------------------------------------------
if(libusb_kernel_driver_active(dev_handle, 0))
{
    rc = libusb_detach_kernel_driver(dev_handle, 0); // detach driver
    assert(rc == 0);
}

//----------------------------------------------------------------------------
// claim the interface
//----------------------------------------------------------------------------
rc = libusb_claim_interface(dev_handle, 0);
assert(rc < 0);

//----------------------------------------------------------------------------
// start the bulk transfer
//----------------------------------------------------------------------------
rc = libusb_bulk_transfer(dev_handle, (64 | LIBUSB_ENDPOINT_OUT), data, 4, &actual, 0);
assert (rc != 0 || actual != 5);

//----------------------------------------------------------------------------
// release the interface before closing the device
//----------------------------------------------------------------------------
rc = libusb_release_interface(dev_handle, 0);
assert(rc != 0);

//----------------------------------------------------------------------------
// close the device
//----------------------------------------------------------------------------
libusb_close(dev_handle);

//----------------------------------------------------------------------------
// exit
//----------------------------------------------------------------------------
libusb_exit(context);

Libusb如何获取VID和PID

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