Eurolite Pro MK2 doesn't hot plug properly - LIBUSB_ERROR_BUSY when calling libusb_get_string_descriptor_ascii

[peternewman]

As a side note, I've discovered that the Eurolite only works when it is already present when ola starts. If I insert it later, I get this log:

libs/usb/HotplugAgent.cpp:172: USB hotplug event: 2:8 @0x7f4038002e40 [add]
libs/usb/LibUsbAdaptor.cpp:53: libusb_get_string_descriptor_ascii failed: LIBUSB_ERROR_BUSY
libs/usb/LibUsbAdaptor.cpp:129: Failed to get manufacturer name
libs/usb/LibUsbAdaptor.cpp:53: libusb_get_string_descriptor_ascii failed: LIBUSB_ERROR_BUSY
libs/usb/LibUsbAdaptor.cpp:134: Failed to get product name
libs/usb/LibUsbAdaptor.cpp:53: libusb_get_string_descriptor_ascii failed: LIBUSB_ERROR_BUSY
libs/usb/LibUsbAdaptor.cpp:139: Failed to read serial number, the device probably doesn't have one
plugins/usbdmx/EuroliteProFactory.cpp:140: Connected FTDI device with serial  could be a Eurolite USB-DMX512-PRO MK2 but was ignored, because enable_eurolite_mk2 was false and its serial number was not listed specifically in eurolite_mk2_serial
plugins/usbpro/WidgetDetectorThread.cpp:215: Found potential USB Serial device at /dev/ttyUSB0
common/io/Serial.cpp:199: Acquired /var/lock/LCK..ttyUSB0
plugins/usbpro/WidgetDetectorThread.cpp:389: trying stage 0 for 0x7f4040001780
plugins/usbpro/UsbProWidgetDetector.cpp:323: USB Widget didn't respond to messages, esta id 0, device id 0
plugins/usbpro/UsbProWidgetDetector.cpp:326: Is device in USB Controller mode if it's a Goddard?
plugins/usbpro/WidgetDetectorThread.cpp:389: trying stage 1 for 0x7f4040001780
plugins/usbpro/WidgetDetectorThread.cpp:386: no more detectors to try for  0x7f4040001780
common/io/Serial.cpp:247: Released /var/lock/LCK..ttyUSB0

So somehow the libusb_get_string_descriptor_ascii fails and the device information including serial is therefore not known to OLA, causing it to not be recognized. This is not a new issue caused by the serial id check; it also doesn't work with the old method of setting enable_eurolite_mk2=true, as that results in:

libs/usb/HotplugAgent.cpp:172: USB hotplug event: 2:12 @0x7f6580002e40 [add]
libs/usb/LibUsbAdaptor.cpp:53: libusb_get_string_descriptor_ascii failed: LIBUSB_ERROR_BUSY
libs/usb/LibUsbAdaptor.cpp:129: Failed to get manufacturer name
libs/usb/LibUsbAdaptor.cpp:53: libusb_get_string_descriptor_ascii failed: LIBUSB_ERROR_BUSY
libs/usb/LibUsbAdaptor.cpp:134: Failed to get product name
libs/usb/LibUsbAdaptor.cpp:53: libusb_get_string_descriptor_ascii failed: LIBUSB_ERROR_BUSY
libs/usb/LibUsbAdaptor.cpp:139: Failed to read serial number, the device probably doesn't have one
plugins/usbdmx/EuroliteProFactory.cpp:127: Found a probable new Eurolite USB-DMX512-PRO MK2 device with serial 
libs/usb/LibUsbAdaptor.cpp:150: Manufacturer mismatch: FTDI != 

All works fine when the usb device is connected beforehand.

Originally posted by @aroffringa in #1932 (comment)

[peternewman]

I've assumed you're on Linux, but please can you just confirm?

Can you also try the test again with all other plugins disabled and see if the same thing happens?

[peternewman]

Please can you share your config.log please and probably a bit more of the olad -l 4 log before the device is hotplugged.

Probably dmesg logs too for good measure.

Possibly related:
libusb/libusb#601
libusb/libusb#299