Cypress CyGetSignature ... libusb error is 0 - c

Question

I'm trying to run the test utility included in the Cypress USB-Serial SDK to create a linux USB-Serial applications for the CY7C65215A eventually
I've gone through the top-level README file and built the provided libusb-1.0.9 library required to use the SDK using these instructions.
I followed the rest of the installation instructions pretty straightforward, make the library and then compiled the test utility.
After running the applications using 'sudo', I get the following SDK debug messages.
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
But there are no listed devices.
I tried using GDB to figure out what was causing this error CY: Error in function CyGetSignature ...libusb error is 0! and I got to
this function
cymisc.c
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;
}
}
The error comes specifically from libusb_control_transfer, which returns 0; I can't GBD into that function to see what returns 0. So I tried enabling libusb debugging with putenv( "LIBUSB_DEBUG=4" ); in my main function, and I get these messages that I think are related to my error
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]
This is where I'm stuck, I have a feeling maybe I'm not building/installing the libusb-1.0.9 correctly, but I'm not sure.
The device is connected and functioning, but not visible to the test utility.
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

Answer 1

These should be comments, but I do not have sufficient "reputation" to comment.
libusb_control_transfer() tries to transfer four bytes of payload (CY_GET_SIGNATURE_LEN==4) in an USB control message, but the device returns no payload at all. Even libusb's sync_transfer_cb() agrees.
Personally, this looks like a hardware issue to me, but I know nothing anyway.
Question: Exactly why would you compile libusb-1.0.9 from scratch, and not install it or a later version from the package repository? (In Debian/Ubuntu/Mint, you'd install libusb-1.0-0 and libusb-1.0-0-dev packages.)
As explained in the libcyusbserial github tree, you need either 1.0.9 or later. Current version as of this writing is 1.0.26. (Depending on the age/version of your Linux distribution, you can expect the version in the package management to be anywhere between 1.0.21 and 1.0.26.)
There is nothing in the Changelog that indicates there was a bug related to control transfers that could lead to data being zero, but it is possible.