Add libusb check for known ADALM-Pluto VID:PID

CMakeLists.txt

@@ -62,14 +62,29 @@ if (LibAD9361_FOUND)
     add_definitions(-DHAS_AD9361_IIO)
 endif()
 
+########################################################################
+# Find libusb
+########################################################################
+find_package(LibUSB)
+
+if(LibUSB_FOUND)
+    message(STATUS "LibUSB_INCLUDE_DIRS: ${LibUSB_INCLUDE_DIRS}")
+    message(STATUS "LibUSB_LIBRARIES: ${LibUSB_LIBRARIES}")
+    message(STATUS "LibUSB_DEFINITIONS: ${LibUSB_DEFINITIONS}")
+    include_directories(${LibUSB_INCLUDE_DIRS})
+    add_definitions(-DHAS_LIBUSB1)
+    #disable warnings for libusb.h
+    add_compile_options($<$<CXX_COMPILER_ID:GNU,Clang,AppleClang>:-Wno-zero-length-array>)
+endif()
+
 
 SOAPY_SDR_MODULE_UTIL(
     TARGET PlutoSDRSupport
     SOURCES
     PlutoSDR_Registration.cpp
     PlutoSDR_Settings.cpp
     PlutoSDR_Streaming.cpp
-    LIBRARIES ${LibIIO_LIBRARIES} ${LibAD9361_LIBRARIES}
+    LIBRARIES ${LibIIO_LIBRARIES} ${LibAD9361_LIBRARIES} ${LIBUSB_LIBRARIES}
 )
 
 ########################################################################

FindLibAD9361.cmake

@@ -1,10 +1,11 @@
 # - Try to find libad9361-iio
 # Once done this will define
 #
-#  LibAD9361_FOUND - system has libiio
-#  LibAD9361_INCLUDE_DIRS - the libiio include directory
-#  LibAD9361_LIBRARIES - Link these to use libiio
-#  LibAD9361_DEFINITIONS - Compiler switches required for using libiio
+#  LibAD9361_FOUND - system has libad9361
+#  LibAD9361_INCLUDE_DIRS - the libad9361 include directory
+#  LibAD9361_LIBRARIES - Link these to use libad9361
+#  LibAD9361_DEFINITIONS - Compiler switches required for using libad9361
+#  LibAD9361_VERSION - the libad9361 version
 #
 # Redistribution and use is allowed according to the terms of the New BSD license.
 # For details see the accompanying COPYING-CMAKE-SCRIPTS file.

FindLibIIO.cmake

@@ -5,6 +5,7 @@
 #  LibIIO_INCLUDE_DIRS - the libiio include directory
 #  LibIIO_LIBRARIES - Link these to use libiio
 #  LibIIO_DEFINITIONS - Compiler switches required for using libiio
+#  LibIIO_VERSION - the libiio version
 #
 # Redistribution and use is allowed according to the terms of the New BSD license.
 # For details see the accompanying COPYING-CMAKE-SCRIPTS file.

FindLibUSB.cmake

@@ -0,0 +1,54 @@
+# - Try to find LibUSB-1.0
+# Once done this will define
+#
+#  LibUSB_FOUND - System has libusb
+#  LibUSB_INCLUDE_DIRS - The libusb include directories
+#  LibUSB_LIBRARIES - The libraries needed to use libusb
+#  LibUSB_DEFINITIONS - Compiler switches required for using libusb
+#  LibUSB_VERSION - the libusb version
+#
+
+find_package(PkgConfig)
+pkg_check_modules(PC_LibUSB QUIET libusb-1.0)
+set(LibUSB_DEFINITIONS ${PC_LibUSB_CFLAGS_OTHER})
+
+find_path(LibUSB_INCLUDE_DIR NAMES libusb.h
+          HINTS ${PC_LibUSB_INCLUDE_DIRS}
+          PATH_SUFFIXES libusb-1.0
+          PATHS
+          /usr/include
+          /usr/local/include )
+
+#standard library name for libusb-1.0
+set(libusb1_library_names usb-1.0)
+
+#libusb-1.0 compatible library on freebsd
+if((CMAKE_SYSTEM_NAME STREQUAL "FreeBSD") OR (CMAKE_SYSTEM_NAME STREQUAL "kFreeBSD"))
+    list(APPEND libusb1_library_names usb)
+endif()
+
+#libusb-1.0 name on Windows (from PothosSDR distribution)
+if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+    list(APPEND libusb1_library_names libusb-1.0)
+endif()
+
+find_library(LibUSB_LIBRARY
+             NAMES ${libusb1_library_names}
+             HINTS ${PC_LibUSB_LIBRARY_DIRS}
+             PATHS
+             /usr/lib
+             /usr/local/lib )
+
+set(LibUSB_VERSION ${PC_LibUSB_VERSION})
+
+include(FindPackageHandleStandardArgs)
+# handle the QUIETLY and REQUIRED arguments and set LibUSB_FOUND to TRUE
+# if all listed variables are TRUE
+find_package_handle_standard_args(LibUSB
+                                  REQUIRED_VARS LibUSB_LIBRARY LibUSB_INCLUDE_DIR
+                                  VERSION_VAR LibUSB_VERSION)
+
+mark_as_advanced(LibUSB_LIBRARY LibUSB_INCLUDE_DIR LibUSB_VERSION)
+
+set(LibUSB_LIBRARIES ${LibUSB_LIBRARY} )
+set(LibUSB_INCLUDE_DIRS ${LibUSB_INCLUDE_DIR} )

PlutoSDR_Registration.cpp

@@ -1,6 +1,11 @@
 #include "SoapyPlutoSDR.hpp"
 #include <SoapySDR/Registry.hpp>
 #include <sstream>
+#include <chrono>
+#include <thread>
+#ifdef HAS_LIBUSB1
+#include <libusb.h>
+#endif
 
 static std::vector<SoapySDR::Kwargs> results;
 static std::vector<SoapySDR::Kwargs> find_PlutoSDR(const SoapySDR::Kwargs &args) {
@@ -15,9 +20,62 @@ static std::vector<SoapySDR::Kwargs> find_PlutoSDR(const SoapySDR::Kwargs &args)
 	SoapySDR::Kwargs options;
 
 	// Backends can error, scan each one individually
-	std::vector<std::string> backends = {"local", "usb", "ip"};
+	// The filtered "usb" backend is available starting from Libiio 0.24
+	std::vector<std::string> backends = {"local", "usb=0456:b673", "ip"};
 	for (std::vector<std::string>::iterator it = backends.begin(); it != backends.end(); it++) {
 
+		if (*it == "usb=0456:b673") {
+#ifdef HAS_LIBUSB1
+			// Abort early if no known ADALM-Pluto USB VID:PID (0456:b673) is found,
+			// that way we won't block USB access for other drivers' enumeration on Libiio before 0.24.
+			libusb_context *usb_ctx = nullptr;
+			int r = libusb_init(&usb_ctx);
+			if (r < 0) {
+				SoapySDR_logf(SOAPY_SDR_WARNING, "libusb init error (%d)\n", r);
+			}
+			else {
+				// This is what libusb_open_device_with_vid_pid(usb_ctx, 0x0456, 0xb673) does,
+				// but without actually opening a device.
+				struct libusb_device **devs;
+				// this is cached in libusb, we won't block USB access for other drivers
+				r = libusb_get_device_list(usb_ctx, &devs);
+				if (r < 0) {
+					SoapySDR_logf(SOAPY_SDR_WARNING, "libusb get device list error (%d)\n", r);
+					continue; // iio scan context will most likely fail too?
+				}
+
+				bool found = false;
+				struct libusb_device *dev;
+				size_t i = 0;
+				while ((dev = devs[i++]) != NULL) {
+					struct libusb_device_descriptor desc;
+					// this is cached in libusb, we won't block USB access for other drivers
+					r = libusb_get_device_descriptor(dev, &desc);
+					if (r < 0) {
+						break;
+					}
+					if (desc.idVendor == 0x0456 && desc.idProduct == 0xb673) {
+						found = true;
+						break;
+					}
+				}
+
+				libusb_free_device_list(devs, 1);
+
+				if (found) {
+					SoapySDR_logf(SOAPY_SDR_DEBUG, "ADALM-Pluto VID:PID found");
+				}
+				else {
+					SoapySDR_logf(SOAPY_SDR_DEBUG, "No ADALM-Pluto VID:PID found");
+					continue;
+				}
+			}
+#endif
+			// Defer to other drivers, prevent a race condition on USB enumeration with Libiio before 0.24,
+			// the value of 500ms has not been confirmed and might be 50ms to 1s possibly.
+			std::this_thread::sleep_for(std::chrono::milliseconds(500));
+		}
+
 		scan_ctx = iio_create_scan_context(it->c_str(), 0);
 		if (scan_ctx == nullptr) {
 			SoapySDR_logf(SOAPY_SDR_WARNING, "Unable to setup %s scan\n", it->c_str());