使用Cypress USB-Serial SDK测试CY7C65215A遇libusb错误0求助

我正尝试使用Cypress USB-Serial SDK附带的测试工具，最终为CY7C65215A开发Linux USB串口应用。已完成以下操作：

• 通读顶层README文件
• 按说明构建SDK所需的libusb-1.0.9库
• 编译测试工具

错误现象 #

使用sudo运行测试工具后，输出如下SDK调试信息，但无设备被列出：

CY:Kernel driver active on the interface number 0 
CY:Info The total number of endpoints are 2 
CY:Info The Endpoints are in 131 and out 1 and interrup 138
CY:Info The device type is 0 
CY: Error in function CyGetSignature ...libusb error is 0!
CY:Kernel driver active on the interface number 0 
CY:Kernel driver active on the interface number 0 
CY:Kernel driver active on the interface number 0 
CY:Kernel driver active on the interface number 0 
CY:Kernel driver active on the interface number 0 
CY:Kernel driver active on the interface number 0 

代码定位 #

通过GDB定位到错误来自CY: Error in function CyGetSignature ...libusb error is 0!，对应cymisc.c中的CyGetSignature函数：

CY_RETURN_STATUS CyGetSignature (
        CY_HANDLE handle,
        UCHAR *signature
        )
{
    UINT16 wValue, wIndex, wLength;
    UINT8 bmRequestType, bmRequest;
    int rStatus, ioTimeout = CY_USB_SERIAL_TIMEOUT;
    CY_DEVICE *device;
    libusb_device_handle *devHandle;

    if (handle == NULL)
        return CY_ERROR_INVALID_HANDLE;
    device = (CY_DEVICE *)handle;
    devHandle = device->devHandle;

    bmRequestType = CY_VENDOR_REQUEST_DEVICE_TO_HOST;
    bmRequest = CY_GET_SIGNATURE_CMD; 
    wValue = 0x00;
    wIndex = 0x00;
    wLength = CY_GET_SIGNATURE_LEN;

    rStatus = libusb_control_transfer (devHandle, bmRequestType, bmRequest,
            wValue, wIndex, (unsigned char*)signature, wLength, ioTimeout);
    if (rStatus > 0){
        return CY_SUCCESS;
    }
    else if (rStatus == LIBUSB_ERROR_TIMEOUT){
        CY_DEBUG_PRINT_ERROR ("CY:Time out error ..function is %s \n", __func__);
        return CY_ERROR_IO_TIMEOUT;
    }
    else {
        CY_DEBUG_PRINT_ERROR ("CY: Error in function %s ...libusb error is %d!\n", __func__, rStatus);
        return CY_ERROR_REQUEST_FAILED;
    }
}

错误具体来自返回0的libusb_control_transfer，无法通过GDB进入该函数查看内部原因。

libusb调试输出 #

在主函数中添加putenv( "LIBUSB_DEBUG=4" );开启libusb调试，得到以下信息：

CY:Info The total number of endpoints are 2 
CY:Info The Endpoints are in 131 and out 1 and interrup 39
[ 0.202464] [0000374a] libusb: debug [libusb_get_config_descriptor] index 0
CY:Info The device type is 0 
[ 0.202479] [0000374a] libusb: debug [libusb_alloc_transfer] transfer 0x5572788007c8
[ 0.202486] [0000374a] libusb: debug [libusb_submit_transfer] transfer 0x5572788007c8
[ 0.202494] [0000374a] libusb: debug [add_to_flying_list] arm timer for timeout in 5000ms (first in line)
[ 0.202528] [0000374a] libusb: debug [libusb_handle_events_timeout_completed] doing our own event handling
[ 0.202535] [0000374a] libusb: debug [handle_events] event sources modified, reallocating event data
[ 0.202544] [0000374a] libusb: debug [usbi_wait_for_events] poll() 3 fds with timeout in 60000ms
[ 0.202704] [0000374a] libusb: debug [usbi_wait_for_events] poll() returned 1
[ 0.202711] [0000374a] libusb: debug [reap_for_handle] urb type=2 status=0 transferred=0
[ 0.202714] [0000374a] libusb: debug [handle_control_completion] handling completion status 0
[ 0.202717] [0000374a] libusb: debug [arm_timer_for_next_timeout] no timeouts, disarming timer
[ 0.202721] [0000374a] libusb: debug [usbi_handle_transfer_completion] transfer 0x5572788007c8 has callback 0x7fc6a5b16dd0
[ 0.202724] [0000374a] libusb: debug [sync_transfer_cb] actual_length=0
[ 0.202728] [0000374a] libusb: debug [libusb_free_transfer] transfer 0x5572788007c8
CY: Error in function CyGetSignature ...libusb error is 0!
[ 0.202738] [0000374a] libusb: debug [libusb_close]

设备状态确认 #

当前怀疑libusb-1.0.9的构建或安装存在问题，但无法确定。设备已正常连接，在lsusb中可见：

Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 002: ID 27c6:609c Shenzhen Goodix Technology Co.,Ltd. Goodix USB2.0 MISC
Bus 003 Device 003: ID 8087:0032 Intel Corp. 
Bus 003 Device 004: ID 04b4:0005 Cypress Semiconductor Corp. USB-Serial (Dual Channel)
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 004: ID 090c:3350 Silicon Motion, Inc. - Taiwan (formerly Feiya Technology Corp.) USB DISK
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

内容的提问来源于stack exchange，提问作者misguidedsquid