I'm using a linux OS and was wondering if there were any file descriptors I could poll/select which would trigger when data was waiting to be read from a usb device. I am also using the libusb library and have yet to find file descriptors which I can use.
Use libusb's polling functions to hook its file descriptors into your event loop. select will wake up whenever there's activity that libusb will need to handle, which includes but probably is not limited to data being available for reading.