usb: work on libusb code to use a single context across all calls

libusb allocation stuff had been moved inside of smart pointer classes to handle automatic cleanup

the public device handle implementation now holds an actual libusb device inside of it

needs testing - all platforms

7 files changed, 367 insertions, 366 deletions

diff --git a/host/include/uhd/transport/usb_device_handle.hpp b/host/include/uhd/transport/usb_device_handle.hpp
index 735a3acbe..9bb7db9c4 100644
--- a/host/include/uhd/transport/usb_device_handle.hpp
+++ b/host/include/uhd/transport/usb_device_handle.hpp
@@ -61,12 +61,6 @@ public:
     virtual boost::uint16_t get_product_id() const = 0;
 
     /*!
-     * Return the device's USB address
-     * \return a Product ID
-     */
-    virtual boost::uint16_t get_device_addr() const = 0;
-
-    /*!
      * Return a vector of USB devices on this host 
      * \return a vector of USB device handles that match vid and pid
      */
diff --git a/host/lib/transport/CMakeLists.txt b/host/lib/transport/CMakeLists.txt
index 48b6e9677..61616d077 100644
--- a/host/lib/transport/CMakeLists.txt
+++ b/host/lib/transport/CMakeLists.txt
@@ -31,7 +31,6 @@ IF(LIBUSB_FOUND)
         ${CMAKE_SOURCE_DIR}/lib/transport/libusb1_zero_copy.cpp
         ${CMAKE_SOURCE_DIR}/lib/transport/libusb1_base.cpp
         ${CMAKE_SOURCE_DIR}/lib/transport/libusb1_base.hpp
-        ${CMAKE_SOURCE_DIR}/lib/transport/libusb1_device_handle.cpp
     )
     IF(MSVC) #include our custom stdint for libusb
         INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR}/lib/transport/msvc)
diff --git a/host/lib/transport/libusb1_base.cpp b/host/lib/transport/libusb1_base.cpp
index cd3e4adcf..5ff996642 100644
--- a/host/lib/transport/libusb1_base.cpp
+++ b/host/lib/transport/libusb1_base.cpp
@@ -17,107 +17,242 @@
 
 #include "libusb1_base.hpp"
 #include <uhd/utils/assert.hpp>
+#include <uhd/types/dict.hpp>
+#include <boost/weak_ptr.hpp>
+#include <boost/foreach.hpp>
 #include <iostream>
 
 using namespace uhd::transport;
 
-/**********************************************************
- * Helper Methods
- **********************************************************/
-
-/**********************************************************
- * libusb namespace 
- **********************************************************/
-void libusb::init(libusb_context **ctx, int debug_level)
-{
-    UHD_ASSERT_THROW(libusb_init(ctx) == 0);
-    libusb_set_debug(*ctx, debug_level);
+/***********************************************************************
+ * libusb session
+ **********************************************************************/
+class libusb_session_impl : public libusb::session{
+public:
+    libusb_session_impl(void){
+        UHD_ASSERT_THROW(libusb_init(&_context) == 0);
+        libusb_set_debug(_context, debug_level);
+    }
+
+    ~libusb_session_impl(void){
+        libusb_exit(_context);
+    }
+
+    libusb_context *get_context(void) const{
+        return _context;
+    }
+
+private:
+    libusb_context *_context;
+};
+
+libusb::session::sptr libusb::session::get_global_session(void){
+    static boost::weak_ptr<session> global_session;
+
+    //not expired -> get existing session
+    if (not global_session.expired()) return global_session.lock();
+
+    //create a new global session
+    sptr new_global_session(new libusb_session_impl());
+    global_session = new_global_session;
+    return new_global_session;
 }
 
-libusb_device_handle *libusb::open_device(libusb_context *ctx,
-                                          usb_device_handle::sptr handle)
-{
-    libusb_device_handle *dev_handle = NULL;
-    libusb_device **libusb_dev_list;
-    size_t dev_cnt = libusb_get_device_list(ctx, &libusb_dev_list);
+/***********************************************************************
+ * libusb device
+ **********************************************************************/
+class libusb_device_impl : public libusb::device{
+public:
+    libusb_device_impl(libusb_device *dev){
+        _session = libusb::session::get_global_session();
+        _dev = dev;
+    }
 
-    //find and open the USB device 
-    for (size_t i = 0; i < dev_cnt; i++) {
-        libusb_device *dev = libusb_dev_list[i];
+    ~libusb_device_impl(void){
+        libusb_unref_device(this->get());
+    }
 
-        if (compare_device(dev, handle)) {
-            if (libusb_open(dev, &dev_handle) == 0) break;
-        }
+    libusb_device *get(void) const{
+        return _dev;
     }
 
-    libusb_free_device_list(libusb_dev_list, true);
-    if(dev_handle == NULL)
-        throw std::runtime_error("USB: cannot open device handle");
-    return dev_handle;
-}
+private:
+    libusb::session::sptr _session; //always keep a reference to session
+    libusb_device *_dev;
+};
+
+/***********************************************************************
+ * libusb device list
+ **********************************************************************/
+class libusb_device_list_impl : public libusb::device_list{
+public:
+    libusb_device_list_impl(void){
+        libusb::session::sptr sess = libusb::session::get_global_session();
 
-//note: changed order of checks so it only tries to get_serial and get_device_address if vid and pid match
-//doing this so it doesn't try to open the device if it's not ours
-bool libusb::compare_device(libusb_device *dev,
-                            usb_device_handle::sptr handle)
-{
-    std::string serial         = handle->get_serial();
-    boost::uint16_t vendor_id  = handle->get_vendor_id();
-    boost::uint16_t product_id = handle->get_product_id();
-    boost::uint16_t device_addr = handle->get_device_addr();
-
-    libusb_device_descriptor libusb_desc;
-    if (libusb_get_device_descriptor(dev, &libusb_desc) != 0)
-        return false;
-    if (vendor_id != libusb_desc.idVendor)
-        return false;
-    if (product_id != libusb_desc.idProduct)
-        return false;
-    if (serial != get_serial(dev))
-        return false;
-    if (device_addr != libusb_get_device_address(dev))
-        return false;
-
-    return true;
+        //allocate a new list of devices
+        libusb_device** dev_list;
+        ssize_t ret = libusb_get_device_list(sess->get_context(), &dev_list);
+        if (ret < 0) throw std::runtime_error("cannot enumerate usb devices");
+
+        //fill the vector of device references
+        for (size_t i = 0; i < size_t(ret); i++) _devs.push_back(
+            libusb::device::sptr(new libusb_device_impl(dev_list[i]))
+        );
+
+        //free the device list but dont unref (done in ~device)
+        libusb_free_device_list(dev_list, false/*dont unref*/);
+    }
+
+    size_t size(void) const{
+        return _devs.size();
+    }
+
+    libusb::device::sptr at(size_t i) const{
+        return _devs.at(i);
+    }
+
+private:
+    std::vector<libusb::device::sptr> _devs;
+};
+
+libusb::device_list::sptr libusb::device_list::make(void){
+    return sptr(new libusb_device_list_impl());
 }
 
+/***********************************************************************
+ * libusb device descriptor
+ **********************************************************************/
+class libusb_device_descriptor_impl : public libusb::device_descriptor{
+public:
+    libusb_device_descriptor_impl(libusb::device::sptr dev){
+        _dev = dev;
+        UHD_ASSERT_THROW(libusb_get_device_descriptor(_dev->get(), &_desc) == 0);
+    }
 
-bool libusb::open_interface(libusb_device_handle *dev_handle,
-                            int interface)
-{
-    int ret = libusb_claim_interface(dev_handle, interface);
-    if (ret < 0) {
-        std::cerr << "error: libusb_claim_interface() " << ret << std::endl;
-        return false;
+    const libusb_device_descriptor &get(void) const{
+        return _desc;
     }
-    else {
-        return true;
+
+    std::string get_ascii_serial(void) const{
+        if (this->get().iSerialNumber == 0) return "";
+
+        libusb::device_handle::sptr handle(
+            libusb::device_handle::get_cached_handle(_dev)
+        );
+
+        unsigned char buff[512];
+        ssize_t ret = libusb_get_string_descriptor_ascii(
+            handle->get(), this->get().iSerialNumber, buff, sizeof(buff)
+        );
+        if (ret < 0) return ""; //on error, just return empty string
+
+        return std::string((char *)buff, ret);
     }
+
+private:
+    libusb::device::sptr _dev; //always keep a reference to device
+    libusb_device_descriptor _desc;
+};
+
+libusb::device_descriptor::sptr libusb::device_descriptor::make(device::sptr dev){
+    return sptr(new libusb_device_descriptor_impl(dev));
 }
 
+/***********************************************************************
+ * libusb device handle
+ **********************************************************************/
+class libusb_device_handle_impl : public libusb::device_handle{
+public:
+    libusb_device_handle_impl(libusb::device::sptr dev){
+        _dev = dev;
+        UHD_ASSERT_THROW(libusb_open(_dev->get(), &_handle) == 0);
+    }
+
+    ~libusb_device_handle_impl(void){
+        //release all claimed interfaces
+        for (size_t i = 0; i < _claimed.size(); i++){
+            libusb_release_interface(this->get(), _claimed[i]);
+        }
+        libusb_close(_handle);
+    }
+
+    libusb_device_handle *get(void) const{
+        return _handle;
+    }
 
-std::string libusb::get_serial(libusb_device *dev)
-{
-    unsigned char buff[32];
+    void claim_interface(int interface){
+        UHD_ASSERT_THROW(libusb_claim_interface(this->get(), interface) == 0);
+        _claimed.push_back(interface);
+    }
 
-    libusb_device_descriptor desc;
-    if (libusb_get_device_descriptor(dev, &desc) < 0)
-        return "";
+private:
+    libusb::device::sptr _dev; //always keep a reference to device
+    libusb_device_handle *_handle;
+    std::vector<int> _claimed;
+};
 
-    if (desc.iSerialNumber == 0)
-        return "";
+libusb::device_handle::sptr libusb::device_handle::get_cached_handle(device::sptr dev){
+    static uhd::dict<libusb_device *, boost::weak_ptr<device_handle> > handles;
 
-    //open the device because we have to
-    libusb_device_handle *dev_handle;
-    if (libusb_open(dev, &dev_handle) < 0)
-        return "";
+    //not expired -> get existing session
+    if (handles.has_key(dev->get()) and not handles[dev->get()].expired()){
+        return handles[dev->get()].lock();
+    }
 
-    if (libusb_get_string_descriptor_ascii(dev_handle, desc.iSerialNumber,
-                                           buff, sizeof(buff)) < 0) {
-        return "";
+    //create a new global session
+    sptr new_handle(new libusb_device_handle_impl(dev));
+    handles[dev->get()] = new_handle;
+    return new_handle;
+}
+
+/***********************************************************************
+ * libusb special handle
+ **********************************************************************/
+class libusb_special_handle_impl : public libusb::special_handle{
+public:
+    libusb_special_handle_impl(libusb::device::sptr dev){
+        _dev = dev;
     }
 
-    libusb_close(dev_handle);
+    libusb::device::sptr get_device(void) const{
+        return _dev;
+    }
+
+    std::string get_serial(void) const{
+        return libusb::device_descriptor::make(this->get_device())->get_ascii_serial();
+    }
+
+    boost::uint16_t get_vendor_id(void) const{
+        return libusb::device_descriptor::make(this->get_device())->get().idVendor;
+    }
+
+    boost::uint16_t get_product_id(void) const{
+        return libusb::device_descriptor::make(this->get_device())->get().idProduct;
+    }
+
+private:
+    libusb::device::sptr _dev; //always keep a reference to device
+};
+
+libusb::special_handle::sptr libusb::special_handle::make(device::sptr dev){
+    return sptr(new libusb_special_handle_impl(dev));
+}
+
+/***********************************************************************
+ * list device handles implementations
+ **********************************************************************/
+std::vector<usb_device_handle::sptr> usb_device_handle::get_device_list(
+    boost::uint16_t vid, boost::uint16_t pid
+){
+    std::vector<usb_device_handle::sptr> handles;
+
+    libusb::device_list::sptr dev_list = libusb::device_list::make();
+    for (size_t i = 0; i < dev_list->size(); i++){
+        usb_device_handle::sptr handle = libusb::special_handle::make(dev_list->at(i));
+        if (handle->get_vendor_id() == vid and handle->get_product_id() == pid){
+            handles.push_back(handle);
+        }
+    }
 
-    return (char*) buff;
+    return handles;
 }
diff --git a/host/lib/transport/libusb1_base.hpp b/host/lib/transport/libusb1_base.hpp
index 484bcf3d9..47d078cde 100644
--- a/host/lib/transport/libusb1_base.hpp
+++ b/host/lib/transport/libusb1_base.hpp
@@ -19,74 +19,122 @@
 #define INCLUDED_LIBUHD_TRANSPORT_LIBUSB_HPP
 
 #include <uhd/config.hpp>
+#include <boost/utility.hpp>
+#include <boost/shared_ptr.hpp>
 #include <uhd/transport/usb_device_handle.hpp>
 #include <libusb-1.0/libusb.h>
 
 namespace uhd { namespace transport {
 
 namespace libusb {
-    /*
-     * Initialize libusb and set debug level
-     * Takes a pointer to context pointer because that's
-     * how libusb rolls. Debug levels.
-     *     
-     *   Level 0: no messages ever printed by the library (default)
-     *   Level 1: error messages are printed to stderr
-     *   Level 2: warning and error messages are printed to stderr
-     *   Level 3: informational messages are printed to stdout, warning
-     *            and error messages are printed to stderr
-     *
-     * \param ctx pointer to context pointer
-     * \param debug_level
+
+    /*!
+     * This session class holds a global libusb context for this process.
+     * The get global session call will create a new context if none exists.
+     * When all references to session are destroyed, the context will be freed.
      */
-    void init(libusb_context **ctx, int debug_level);
-
-    /*
-     * Open the device specified by a generic handle
-     * Find the libusb_device cooresponding to the generic handle
-     * and open it for I/O, which returns a libusb_device_handle
-     * ready for an interface
-     * \param ctx the libusb context used for init
-     * \return a libusb_device_handle ready for action 
+    class session : boost::noncopyable {
+    public:
+        typedef boost::shared_ptr<session> sptr;
+
+        /*!
+         *   Level 0: no messages ever printed by the library (default)
+         *   Level 1: error messages are printed to stderr
+         *   Level 2: warning and error messages are printed to stderr
+         *   Level 3: informational messages are printed to stdout, warning
+         *            and error messages are printed to stderr
+         */
+        static const int debug_level = 0;
+
+        //! get a shared pointer to the global session
+        static sptr get_global_session(void);
+
+        //! get the underlying libusb context pointer
+        virtual libusb_context *get_context(void) const = 0;
+    };
+
+    /*!
+     * Holds a device pointer with a reference to the session.
      */
-    libusb_device_handle *open_device(libusb_context *ctx,
-                                      usb_device_handle::sptr handle);
-
-    /*
-     * Compare a libusb device with a generic handle 
-     * Check the descriptors and open the device to check the
-     * serial number string. Compare values against the given
-     * handle. The libusb context is already implied in the
-     * libusb_device.
-     * \param dev a libusb_device pointer
-     * \param handle a generic handle specifier
-     * \return true if handle and device match, false otherwise
+    class device : boost::noncopyable {
+    public:
+        typedef boost::shared_ptr<device> sptr;
+
+        //! get the underlying device pointer
+        virtual libusb_device *get(void) const = 0;
+    };
+
+    /*!
+     * This device list class holds a device list that will be
+     * automatically freed when the last reference is destroyed.
      */
-    bool compare_device(libusb_device *dev, usb_device_handle::sptr handle);
-
-    /*
-     * Open an interface to the device
-     * This is a logical operation for operating system housekeeping as
-     * nothing is sent over the bus. The interface much correspond
-     * to the USB device descriptors.
-     * \param dev_handle libusb handle to an opened device
-     * \param interface integer of the interface to use
-     * \return true on success, false on error
+    class device_list : boost::noncopyable {
+    public:
+        typedef boost::shared_ptr<device_list> sptr;
+
+        //! make a new device list
+        static sptr make(void);
+
+        //! the number of devices in this list
+        virtual size_t size() const = 0;
+
+        //! get the device pointer at a particular index
+        virtual device::sptr at(size_t index) const = 0;
+    };
+
+    /*!
+     * Holds a device descriptor and a reference to the device.
      */
-    bool open_interface(libusb_device_handle *dev_handle, int interface);
-
-    /*
-     * Get serial number 
-     * The standard USB device descriptor contains an index to an
-     * actual serial number string descriptor. The index is readily
-     * readble, but the string descriptor requires probing the device.
-     * Because this call attempts to open the device, it may not
-     * succeed because not all USB devices are readily opened.
-     * The default language is used for the request (English).
-     * \param dev a libusb_device pointer
-     * \return string serial number or 0 on error or unavailablity
+    class device_descriptor : boost::noncopyable {
+    public:
+        typedef boost::shared_ptr<device_descriptor> sptr;
+
+        //! make a new descriptor from a device reference
+        static sptr make(device::sptr);
+
+        //! get the underlying device descriptor
+        virtual const libusb_device_descriptor &get(void) const = 0;
+
+        virtual std::string get_ascii_serial(void) const = 0;
+    };
+
+    /*!
+     * Holds a device handle and a reference to the device.
      */
-    std::string get_serial(libusb_device *dev);
+    class device_handle : boost::noncopyable {
+    public:
+        typedef boost::shared_ptr<device_handle> sptr;
+
+        //! get a cached handle or make a new one given the device
+        static sptr get_cached_handle(device::sptr);
+
+        //! get the underlying device handle
+        virtual libusb_device_handle *get(void) const = 0;
+
+        /*!
+         * Open USB interfaces for control using magic value
+         * IN interface:      2
+         * OUT interface:     1
+         * Control interface: 0
+         */
+        virtual void claim_interface(int) = 0;
+    };
+
+    /*!
+     * The special handle is our internal implementation of the
+     * usb device handle which is used publicly to identify a device.
+     */
+    class special_handle : public usb_device_handle {
+    public:
+        typedef boost::shared_ptr<special_handle> sptr;
+
+        //! make a new special handle from device
+        static sptr make(device::sptr);
+
+        //! get the underlying device reference
+        virtual device::sptr get_device(void) const = 0;
+    };
+
 }
 
 }} //namespace
diff --git a/host/lib/transport/libusb1_control.cpp b/host/lib/transport/libusb1_control.cpp
index be9b51111..c989a788c 100644
--- a/host/lib/transport/libusb1_control.cpp
+++ b/host/lib/transport/libusb1_control.cpp
@@ -20,7 +20,6 @@
 
 using namespace uhd::transport;
 
-const int libusb_debug_level = 0;
 const int libusb_timeout = 0;
 
 /***********************************************************************
@@ -28,69 +27,38 @@ const int libusb_timeout = 0;
  **********************************************************************/
 class libusb_control_impl : public usb_control {
 public:
-    libusb_control_impl(usb_device_handle::sptr handle);
-    ~libusb_control_impl();
+    libusb_control_impl(libusb::device_handle::sptr handle):
+        _handle(handle)
+    {
+        _handle->claim_interface(0 /* control interface */);
+    }
 
     size_t submit(boost::uint8_t request_type,
                   boost::uint8_t request,
                   boost::uint16_t value,
                   boost::uint16_t index,
                   unsigned char *buff,
-                  boost::uint16_t length); 
+                  boost::uint16_t length
+    ){
+        return libusb_control_transfer(_handle->get(),
+                                       request_type,
+                                       request,
+                                       value,
+                                       index,
+                                       buff,
+                                       length,
+                                       libusb_timeout);
+    }
 
 private:
-    libusb_context       *_ctx;
-    libusb_device_handle *_dev_handle;
+    libusb::device_handle::sptr _handle;
 };
 
-
-libusb_control_impl::libusb_control_impl(usb_device_handle::sptr handle)
-{
-    _ctx = NULL;
-    libusb::init(&_ctx, libusb_debug_level);
-
-    // Find and open the libusb_device corresponding to the
-    // given handle and return the libusb_device_handle
-    // that can be used for I/O purposes.
-    _dev_handle = libusb::open_device(_ctx, handle);
-
-    // Open USB interfaces for control using magic value
-    // IN interface:      2
-    // OUT interface:     1
-    // Control interface: 0
-    libusb::open_interface(_dev_handle, 0);
-}
-
-
-libusb_control_impl::~libusb_control_impl()
-{
-    libusb_close(_dev_handle);
-    libusb_exit(_ctx);
-}
-
-
-size_t libusb_control_impl::submit(boost::uint8_t request_type,
-                                   boost::uint8_t request,
-                                   boost::uint16_t value,
-                                   boost::uint16_t index, 
-                                   unsigned char *buff,
-                                   boost::uint16_t length) 
-{
-    return libusb_control_transfer(_dev_handle,
-                                   request_type,
-                                   request,
-                                   value,
-                                   index,
-                                   buff, 
-                                   length, 
-                                   libusb_timeout);
-}
-
-
 /***********************************************************************
  * USB control public make functions
  **********************************************************************/
-usb_control::sptr usb_control::make(usb_device_handle::sptr handle)
-{
-    return sptr(new libusb_control_impl(handle));
+usb_control::sptr usb_control::make(usb_device_handle::sptr handle){
+    return sptr(new libusb_control_impl(libusb::device_handle::get_cached_handle(
+        boost::static_pointer_cast<libusb::special_handle>(handle)->get_device()
+    )));
 }
diff --git a/host/lib/transport/libusb1_device_handle.cpp b/host/lib/transport/libusb1_device_handle.cpp
deleted file mode 100644
index 6bef37ed2..000000000
--- a/host/lib/transport/libusb1_device_handle.cpp
+++ /dev/null
@@ -1,118 +0,0 @@
-//
-// Copyright 2010 Ettus Research LLC
-//
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
-//
-
-#include "libusb1_base.hpp"
-#include <uhd/utils/assert.hpp>
-#include <iostream>
-
-using namespace uhd::transport;
-
-const int libusb_debug_level = 0;
-
-/****************************************************************
- * libusb USB device handle implementation class
- ***************************************************************/
-class libusb1_device_handle_impl : public usb_device_handle {
-public:
-    libusb1_device_handle_impl(std::string serial,
-                               boost::uint16_t product_id,
-                               boost::uint16_t vendor_id,
-                               boost::uint16_t device_addr)
-      : _serial(serial), _product_id(product_id), 
-        _vendor_id(vendor_id), _device_addr(device_addr)
-    {
-        /* NOP */
-    }
-
-    ~libusb1_device_handle_impl()
-    {
-        /* NOP */
-    }
-
-    std::string get_serial() const
-    {
-        return _serial;
-    }
-
-    boost::uint16_t get_vendor_id() const
-    {
-        return _vendor_id;
-    }
-
-
-    boost::uint16_t get_product_id() const
-    {
-        return _product_id;
-    }
-
-    boost::uint16_t get_device_addr() const
-    {
-        return _device_addr;
-    }
-
-private:
-    std::string     _serial;
-    boost::uint16_t _product_id;
-    boost::uint16_t _vendor_id;
-    boost::uint16_t _device_addr;
-};
-
-
-usb_device_handle::sptr make_usb_device_handle(libusb_device *dev)
-{
-    libusb_device_descriptor desc;
-
-    if (libusb_get_device_descriptor(dev, &desc) < 0) {
-        throw std::runtime_error("USB: failed to get device descriptor");
-    }
-
-    std::string     serial      = libusb::get_serial(dev);
-    boost::uint16_t product_id  = desc.idProduct;
-    boost::uint16_t vendor_id   = desc.idVendor;
-    boost::uint16_t device_addr = libusb_get_device_address(dev);
-
-    return usb_device_handle::sptr(new libusb1_device_handle_impl(
-        serial,
-        product_id,
-        vendor_id,
-        device_addr));
-}
-
-std::vector<usb_device_handle::sptr> usb_device_handle::get_device_list(boost::uint16_t vid, boost::uint16_t pid)
-{
-    libusb_context *ctx = NULL;
-    libusb_device** libusb_device_list;
-    std::vector<usb_device_handle::sptr> device_handle_list;
-    libusb_device_descriptor desc;
-
-    libusb::init(&ctx, libusb_debug_level);
-
-    size_t dev_size = libusb_get_device_list(ctx, &libusb_device_list);
-    for (size_t i = 0; i < dev_size; i++) {
-        libusb_device *dev = libusb_device_list[i];
-        if(libusb_get_device_descriptor(dev, &desc) != 0) {
-            continue; //just try the next device, do not throw
-        }
-        if(desc.idVendor == vid && desc.idProduct == pid) {
-            device_handle_list.push_back(make_usb_device_handle(dev));
-        }
-    }
-
-    libusb_free_device_list(libusb_device_list, true);
-    libusb_exit(ctx);
-    return device_handle_list; 
-}
diff --git a/host/lib/transport/libusb1_zero_copy.cpp b/host/lib/transport/libusb1_zero_copy.cpp
index b3a160462..41cd4b3fc 100644
--- a/host/lib/transport/libusb1_zero_copy.cpp
+++ b/host/lib/transport/libusb1_zero_copy.cpp
@@ -24,7 +24,6 @@
 
 using namespace uhd::transport;
 
-const int libusb_debug_level = 0;
 const int libusb_timeout = 0;
 
 /***********************************************************************
@@ -57,8 +56,8 @@ void pp_transfer(libusb_transfer *lut)
  **********************************************************************/
 class usb_endpoint {
 private:
-    libusb_device_handle *_dev_handle;
-    libusb_context *_ctx;
+    libusb::device_handle::sptr _handle;
+    libusb::session::sptr _session;
     int  _endpoint;
     bool _input;
 
@@ -90,9 +89,8 @@ private:
     void print_transfer_status(libusb_transfer *lut);
 
 public:
-    usb_endpoint(libusb_device_handle *dev_handle,
-                 libusb_context *ctx, int endpoint, bool input,
-                 size_t transfer_size, size_t num_transfers);
+    usb_endpoint(libusb::device_handle::sptr handle, libusb::session::sptr sess,
+                 int endpoint, bool input, size_t transfer_size, size_t num_transfers);
 
     ~usb_endpoint();
 
@@ -143,11 +141,11 @@ void usb_endpoint::callback_handle_transfer(libusb_transfer *lut)
  * submit the transfers so that they're ready to return when
  * data is available. 
  */
-usb_endpoint::usb_endpoint(libusb_device_handle *dev_handle,
-                          libusb_context *ctx, int endpoint, bool input,
-                          size_t transfer_size, size_t num_transfers)
-    : _dev_handle(dev_handle),
-      _ctx(ctx), _endpoint(endpoint), _input(input),
+usb_endpoint::usb_endpoint(
+    libusb::device_handle::sptr handle, libusb::session::sptr sess,
+    int endpoint, bool input, size_t transfer_size, size_t num_transfers)
+    : _handle(handle), _session(sess),
+      _endpoint(endpoint), _input(input),
       _transfer_size(transfer_size), _num_transfers(num_transfers)
 {
     unsigned int i;
@@ -203,7 +201,7 @@ libusb_transfer *usb_endpoint::allocate_transfer(int buff_len)
     unsigned int endpoint = ((_endpoint & 0x7f) | (_input ? 0x80 : 0));
 
     libusb_fill_bulk_transfer(lut,                // transfer
-                              _dev_handle,        // dev_handle
+                              _handle->get(),     // dev_handle
                               endpoint,           // endpoint
                               buff,               // buffer
                               buff_len,           // length
@@ -356,7 +354,7 @@ bool usb_endpoint::reap_pending_list()
 {
     int retval;
 
-    if ((retval = libusb_handle_events(_ctx)) < 0) {
+    if ((retval = libusb_handle_events(_session->get_context())) < 0) {
         std::cerr << "error: libusb_handle_events: " << retval << std::endl;
         return false;
     }
@@ -383,7 +381,7 @@ bool usb_endpoint::reap_pending_list_timeout()
 
     size_t pending_list_size = _pending_list.size();
 
-    if ((retval = libusb_handle_events_timeout(_ctx, &tv)) < 0) {
+    if ((retval = libusb_handle_events_timeout(_session->get_context(), &tv)) < 0) {
         std::cerr << "error: libusb_handle_events: " << retval << std::endl;
         return false;
     }
@@ -613,11 +611,8 @@ private:
     usb_endpoint          *_rx_ep;
     usb_endpoint          *_tx_ep;
 
-    // Maintain libusb values
-    libusb_context       *_rx_ctx;
-    libusb_context       *_tx_ctx;
-    libusb_device_handle *_rx_dev_handle;
-    libusb_device_handle *_tx_dev_handle;
+    libusb::device_handle::sptr _handle;
+    libusb::session::sptr _session;
 
     size_t _recv_buff_size;
     size_t _send_buff_size;
@@ -626,7 +621,7 @@ private:
 public:
     typedef boost::shared_ptr<libusb_zero_copy_impl> sptr;
 
-    libusb_zero_copy_impl(usb_device_handle::sptr handle,
+    libusb_zero_copy_impl(libusb::device_handle::sptr handle,
                           unsigned int rx_endpoint,
                           unsigned int tx_endpoint,
                           size_t recv_buff_size,
@@ -646,44 +641,27 @@ public:
  * Initializes libusb, opens devices, and sets up interfaces for I/O.
  * Finally, creates endpoints for asynchronous I/O. 
  */
-libusb_zero_copy_impl::libusb_zero_copy_impl(usb_device_handle::sptr handle,
+libusb_zero_copy_impl::libusb_zero_copy_impl(libusb::device_handle::sptr handle,
                                              unsigned int rx_endpoint,
                                              unsigned int tx_endpoint,
                                              size_t buff_size,
                                              size_t block_size)
- : _rx_ctx(NULL), _tx_ctx(NULL), _rx_dev_handle(NULL), _tx_dev_handle(NULL),
+ : _handle(handle), _session(libusb::session::get_global_session()),
    _recv_buff_size(block_size), _send_buff_size(block_size),
    _num_frames(buff_size / block_size)
 {
-    // Initialize libusb with separate contexts to allow
-    // thread safe operation of transmit and receive 
-    libusb::init(&_rx_ctx, libusb_debug_level);
-    libusb::init(&_tx_ctx, libusb_debug_level);
-
-    UHD_ASSERT_THROW((_rx_ctx != NULL) && (_tx_ctx != NULL));
-
-    // Find and open the libusb_device corresponding to the
-    // given handle and return the libusb_device_handle
-    // that can be used for I/O purposes.
-    _rx_dev_handle = libusb::open_device(_rx_ctx, handle);
-    _tx_dev_handle = libusb::open_device(_tx_ctx, handle);
-
-    // Open USB interfaces for tx/rx using magic values.
-    // IN interface:      2
-    // OUT interface:     1
-    // Control interface: 0
-    libusb::open_interface(_rx_dev_handle, 2);
-    libusb::open_interface(_tx_dev_handle, 1);
-
-    _rx_ep = new usb_endpoint(_rx_dev_handle,  // libusb device_handle
-                              _rx_ctx,         // libusb context
+    _handle->claim_interface(2 /*in interface*/);
+    _handle->claim_interface(1 /*out interface*/);
+
+    _rx_ep = new usb_endpoint(_handle,         // libusb device_handle
+                              _session,        // libusb session w/ context
                               rx_endpoint,     // USB endpoint number
                               true,            // IN endpoint
                               _recv_buff_size, // buffer size per transfer 
                               _num_frames);    // number of libusb transfers
 
-    _tx_ep = new usb_endpoint(_tx_dev_handle,  // libusb device_handle
-                              _tx_ctx,         // libusb context
+    _tx_ep = new usb_endpoint(_handle,         // libusb device_handle
+                              _session,        // libusb session w/ context
                               tx_endpoint,     // USB endpoint number
                               false,           // OUT endpoint
                               _send_buff_size, // buffer size per transfer
@@ -694,13 +672,7 @@ libusb_zero_copy_impl::libusb_zero_copy_impl(usb_device_handle::sptr handle,
 libusb_zero_copy_impl::~libusb_zero_copy_impl()
 {
     delete _rx_ep;
-    delete _tx_ep; 
-
-    libusb_close(_rx_dev_handle);
-    libusb_close(_tx_dev_handle);
-
-    libusb_exit(_rx_ctx);
-    libusb_exit(_tx_ctx);
+    delete _tx_ep;
 }
 
 
@@ -755,7 +727,10 @@ usb_zero_copy::sptr usb_zero_copy::make(usb_device_handle::sptr handle,
                                         size_t block_size)
 
 {
-    return sptr(new libusb_zero_copy_impl(handle,
+    libusb::device_handle::sptr dev_handle(libusb::device_handle::get_cached_handle(
+        boost::static_pointer_cast<libusb::special_handle>(handle)->get_device()
+    ));
+    return sptr(new libusb_zero_copy_impl(dev_handle,
                                           rx_endpoint,
                                           tx_endpoint,
                                           buff_size,