OK, progress. This bug is realated to:
which indicates that there are devices which do not like whatever ClearPipeStallBothEnds() does, and have irreversible USB interface crashes as a result of it. It is not clear whether this call ever really helps anything. If you modify line 1889 of darwin-usb.c in the os/ directory of libusb, to be something like:
kresult = 0 && (*(cInterface->interface))->ClearPipeStallBothEnds(cInterface->interface, pipeRef);
(or just comment out the line and replace it with kresult=0; ), and rebuild libusb and link SoapyLMS7 to the new library, all is well. I don’t know if this is a definitive patch or not. It probably indicates a bug in the FTDI601 controller with respect to having its pipes cleared, but for now this seems OK. At least I suspect it to be mostly harmless.