Merge branch 'master' of ettus.sourcerepo.com:ettus/uhdpriv into tvrx_uhd

1 files changed, 131 insertions, 395 deletions

diff --git a/host/lib/transport/libusb1_zero_copy.cpp b/host/lib/transport/libusb1_zero_copy.cpp
index b890a87f9..b089d11e0 100644
--- a/host/lib/transport/libusb1_zero_copy.cpp
+++ b/host/lib/transport/libusb1_zero_copy.cpp
@@ -17,15 +17,17 @@
 
 #include "libusb1_base.hpp"
 #include <uhd/transport/usb_zero_copy.hpp>
+#include <uhd/transport/bounded_buffer.hpp>
 #include <uhd/utils/assert.hpp>
-#include <boost/asio.hpp>
-#include <boost/format.hpp>
+#include <boost/shared_array.hpp>
+#include <boost/foreach.hpp>
+#include <boost/thread.hpp>
+#include <vector>
 #include <iostream>
 #include <iomanip>
 
 using namespace uhd::transport;
 
-const int libusb_debug_level = 0;
 const int libusb_timeout = 0;
 
 /***********************************************************************
@@ -57,53 +59,57 @@ void pp_transfer(libusb_transfer *lut)
  *   interface provided by the kernel. 
  **********************************************************************/
 class usb_endpoint {
+public:
+    typedef boost::shared_ptr<usb_endpoint> sptr;
+
+    usb_endpoint(
+        libusb::device_handle::sptr handle,
+        int endpoint,
+        bool input,
+        size_t transfer_size,
+        size_t num_transfers
+    );
+
+    ~usb_endpoint(void);
+
+    // Exposed interface for submitting / retrieving transfer buffers
+
+    //! Submit a new transfer that was presumably just filled or emptied.
+    void submit(libusb_transfer *lut);
+
+    /*!
+     * Get an available transfer:
+     * For inputs, this is a just filled transfer.
+     * For outputs, this is a just emptied transfer.
+     * \param timeout_ms the timeout to wait for a lut
+     * \return the transfer pointer or NULL if timeout
+     */
+    libusb_transfer *get_lut_with_wait(size_t timeout_ms = 100);
+
+    //Callback use only
+    void callback_handle_transfer(libusb_transfer *lut);
+
 private:
-    libusb_device_handle *_dev_handle;
-    libusb_context *_ctx;
+    libusb::device_handle::sptr _handle;
     int  _endpoint;
     bool _input;
 
     size_t _transfer_size;
     size_t _num_transfers;
 
-    // Transfer state lists (transfers are free, pending, or completed)
-    std::list<libusb_transfer *>  _free_list;
-    std::list<libusb_transfer *>  _pending_list;
-    std::list<libusb_transfer *>  _completed_list;
+    //! hold a bounded buffer of completed transfers
+    typedef bounded_buffer<libusb_transfer *> lut_buff_type;
+    lut_buff_type::sptr _completed_list;
+
+    //! a list of all transfer structs we allocated
+    std::vector<libusb_transfer *>  _all_luts;
+
+    //! a list of shared arrays for the transfer buffers
+    std::vector<boost::shared_array<boost::uint8_t> > _buffers;
 
     // Calls for processing asynchronous I/O 
     libusb_transfer *allocate_transfer(int buff_len);
-    bool cancel(libusb_transfer *lut);
-    bool cancel_all();
-    bool reap_pending_list();
-    bool reap_pending_list_timeout();
-    bool reap_completed_list();
-
-    // Transfer state manipulators 
-    void free_list_add(libusb_transfer *lut);
-    void pending_list_add(libusb_transfer *lut);
-    void completed_list_add(libusb_transfer *lut);
-    libusb_transfer *free_list_get();
-    libusb_transfer *completed_list_get();
-    bool pending_list_remove(libusb_transfer *lut);
-
-    // Debug use
     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();
-
-    // Exposed interface for submitting / retrieving transfer buffers
-    bool submit(libusb_transfer *lut);
-    libusb_transfer *get_completed_transfer();
-    libusb_transfer *get_free_transfer();
-
-    //Callback use only
-    void callback_handle_transfer(libusb_transfer *lut);
 };
 
 
@@ -116,9 +122,8 @@ public:
  * it from the pending to completed status list.
  * \param lut pointer to libusb_transfer
  */
-static void callback(libusb_transfer *lut)
-{
-    usb_endpoint *endpoint = (usb_endpoint *) lut->user_data; 
+static void callback(libusb_transfer *lut){
+    usb_endpoint *endpoint = (usb_endpoint *) lut->user_data;
     endpoint->callback_handle_transfer(lut);
 }
 
@@ -127,14 +132,9 @@ static void callback(libusb_transfer *lut)
  * Accessor call to allow list access from callback space
  * \param pointer to libusb_transfer
  */
-void usb_endpoint::callback_handle_transfer(libusb_transfer *lut)
-{
-    if (!pending_list_remove(lut)) {
-        std::cerr << "USB: pending remove failed" << std::endl;
-        return;
-    }
-
-    completed_list_add(lut);    
+void usb_endpoint::callback_handle_transfer(libusb_transfer *lut){
+    boost::this_thread::disable_interruption di; //disable because the wait can throw
+    _completed_list->push_with_wait(lut);
 }
 
 
@@ -144,19 +144,28 @@ 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),
-      _transfer_size(transfer_size), _num_transfers(num_transfers)
+usb_endpoint::usb_endpoint(
+    libusb::device_handle::sptr handle,
+    int endpoint,
+    bool input,
+    size_t transfer_size,
+    size_t num_transfers
+):
+    _handle(handle),
+    _endpoint(endpoint),
+    _input(input),
+    _transfer_size(transfer_size),
+    _num_transfers(num_transfers)
 {
-    unsigned int i;
-    for (i = 0; i < _num_transfers; i++) {
-        free_list_add(allocate_transfer(_transfer_size));
+    _completed_list = lut_buff_type::make(num_transfers);
 
-        if (_input)
-            submit(free_list_get());
+    for (size_t i = 0; i < _num_transfers; i++){
+        _all_luts.push_back(allocate_transfer(_transfer_size));
+
+        //input luts are immediately submitted to be filled
+        //output luts go into the completed list as free buffers
+        if (_input) this->submit(_all_luts.back());
+        else _completed_list->push_with_wait(_all_luts.back());
     }
 }
 
@@ -168,22 +177,18 @@ usb_endpoint::usb_endpoint(libusb_device_handle *dev_handle,
  * the transfers. Libusb will deallocate the data buffer held by
  * each transfer.
  */
-usb_endpoint::~usb_endpoint()
-{
-    cancel_all();
-
-    while (!_pending_list.empty()) {
-        if (!reap_pending_list())
-            std::cerr << "error: destructor failed to reap" << std::endl;
+usb_endpoint::~usb_endpoint(void){
+    //cancel all transfers
+    BOOST_FOREACH(libusb_transfer *lut, _all_luts){
+        libusb_cancel_transfer(lut);
     }
 
-    while (!_completed_list.empty()) {
-        if (!reap_completed_list())
-            std::cerr << "error: destructor failed to reap" << std::endl;
-    }
+    //collect canceled transfers (drain the queue)
+    while (this->get_lut_with_wait() != NULL){};
 
-    while (!_free_list.empty()) {
-        libusb_free_transfer(free_list_get());
+    //free all transfers
+    BOOST_FOREACH(libusb_transfer *lut, _all_luts){
+        libusb_free_transfer(lut);
     }
 }
 
@@ -195,20 +200,21 @@ usb_endpoint::~usb_endpoint()
  * \param buff_len size of the individual buffer held by each transfer
  * \return pointer to an allocated libusb_transfer
  */
-libusb_transfer *usb_endpoint::allocate_transfer(int buff_len)
-{
+libusb_transfer *usb_endpoint::allocate_transfer(int buff_len){
     libusb_transfer *lut = libusb_alloc_transfer(0);
 
-    unsigned char *buff = new unsigned char[buff_len];
+    boost::shared_array<boost::uint8_t> buff(new boost::uint8_t[buff_len]);
+    _buffers.push_back(buff); //store a reference to this shared array
 
     unsigned int endpoint = ((_endpoint & 0x7f) | (_input ? 0x80 : 0));
+    libusb_transfer_cb_fn lut_callback = libusb_transfer_cb_fn(&callback);
 
     libusb_fill_bulk_transfer(lut,                // transfer
-                              _dev_handle,        // dev_handle
+                              _handle->get(),     // dev_handle
                               endpoint,           // endpoint
-                              buff,               // buffer
+                              buff.get(),         // buffer
                               buff_len,           // length
-                              callback,           // callback
+                              lut_callback,       // callback
                               this,               // user_data
                               0);                 // timeout
     return lut;
@@ -221,95 +227,15 @@ libusb_transfer *usb_endpoint::allocate_transfer(int buff_len)
  * \param lut pointer to libusb_transfer
  * \return true on success or false on error 
  */
-bool usb_endpoint::submit(libusb_transfer *lut)
-{
-    int retval;
-    if ((retval = libusb_submit_transfer(lut)) < 0) {
-        std::cerr << "error: libusb_submit_transfer: " << retval << std::endl;
-        return false;
-    }
-
-    pending_list_add(lut);
-    return true;
+void usb_endpoint::submit(libusb_transfer *lut){
+    UHD_ASSERT_THROW(libusb_submit_transfer(lut) == 0);
 }
 
-
-/*
- * Cancel a pending transfer 
- * Search the pending list for the transfer and cancel if found.
- * \param lut pointer to libusb_transfer to cancel
- * \return true on success or false if transfer is not found
- *
- * Note: success only indicates submission of cancelation request.
- * Sucessful cancelation is not known until the callback occurs.
- */
-bool usb_endpoint::cancel(libusb_transfer *lut)
-{
-    std::list<libusb_transfer*>::iterator iter;
-    for (iter = _pending_list.begin(); iter != _pending_list.end(); iter++) {
-        if (*iter == lut) { 
-            libusb_cancel_transfer(lut); 
-            return true;
-        }
-    }
-    return false;
-}
-
-
-/*
- * Cancel all pending transfers 
- * \return bool true if cancelation request is submitted
- *
- * Note: success only indicates submission of cancelation request.
- * Sucessful cancelation is not known until the callback occurs.
- */
-bool usb_endpoint::cancel_all()
-{
-    std::list<libusb_transfer*>::iterator iter;
-
-    for (iter = _pending_list.begin(); iter != _pending_list.end(); iter++) {
-        if (libusb_cancel_transfer(*iter) < 0) {
-            std::cerr << "error: libusb_cancal_transfer() failed" << std::endl;
-            return false;
-        }
-    }
-
-    return true;
-}
-
-
-/*
- * Reap completed transfers
- * return true if at least one transfer was reaped, false otherwise. 
- * Check completed transfers for errors and mark as free. This is a
- * blocking call. 
- * \return bool true if a libusb transfer is reaped, false otherwise
- */
-bool usb_endpoint::reap_completed_list()
-{
-    libusb_transfer *lut;
-
-    if (_completed_list.empty()) {
-        if (!reap_pending_list_timeout())
-            return false;
-    }
-
-    while (!_completed_list.empty()) {
-        lut = completed_list_get();
-        print_transfer_status(lut);
-        free_list_add(lut);
-    }
-
-    return true;
-}
-
-
 /*
  * Print status errors of a completed transfer
  * \param lut pointer to an libusb_transfer
  */
-void usb_endpoint::print_transfer_status(libusb_transfer *lut)
-{
+void usb_endpoint::print_transfer_status(libusb_transfer *lut){
     switch (lut->status) {
     case LIBUSB_TRANSFER_COMPLETED:
         if (lut->actual_length < lut->length) {
@@ -345,166 +271,15 @@ void usb_endpoint::print_transfer_status(libusb_transfer *lut)
     }
 }
 
-
-/*
- * Reap pending transfers without timeout 
- * This is a blocking call. Reaping submitted transfers is
- * handled by libusb and the assigned callback function.
- * Block until at least one transfer is reaped.
- * \return true true if a transfer was reaped or false otherwise
- */
-bool usb_endpoint::reap_pending_list()
-{
-    int retval;
-
-    if ((retval = libusb_handle_events(_ctx)) < 0) {
-        std::cerr << "error: libusb_handle_events: " << retval << std::endl;
-        return false;
-    }
-
-    return true;
-}
-
-
-/*
- * Reap pending transfers with timeout 
- * This call blocks until a transfer is reaped or timeout.
- * Reaping submitted transfers is handled by libusb and the
- * assigned callback function. Block until at least one
- * transfer is reaped or timeout occurs.
- * \return true if a transfer was reaped or false otherwise
- */
-bool usb_endpoint::reap_pending_list_timeout()
-{
-    int retval;
-    timeval tv;
-
-    tv.tv_sec = 0;
-    tv.tv_usec = 100000; //100ms
-
-    size_t pending_list_size = _pending_list.size();
-
-    if ((retval = libusb_handle_events_timeout(_ctx, &tv)) < 0) {
-        std::cerr << "error: libusb_handle_events: " << retval << std::endl;
-        return false;
-    }
-
-    if (_pending_list.size() < pending_list_size) {
-        return true;
-    }
-    else {
-        return false;
-    }
-}
-
-
-/*
- * Get a free transfer
- * The transfer has an empty data bufer for OUT requests 
- * \return pointer to a libusb_transfer
- */
-libusb_transfer *usb_endpoint::get_free_transfer()
-{
-    if (_free_list.empty()) {
-        if (!reap_completed_list())
-            return NULL; 
-    }
-
-    return free_list_get();
-}
-
-
-/*
- * Get a completed transfer 
- * The transfer has a full data buffer for IN requests
- * \return pointer to libusb_transfer
- */
-libusb_transfer *usb_endpoint::get_completed_transfer()
-{
-    if (_completed_list.empty()) {
-        if (!reap_pending_list_timeout())
-            return NULL; 
-    }
-
-    return completed_list_get();
-}
-
-/*
- * List operations 
- */
-void usb_endpoint::free_list_add(libusb_transfer *lut)
-{
-    _free_list.push_back(lut);
-}
-
-void usb_endpoint::pending_list_add(libusb_transfer *lut)
-{
-    _pending_list.push_back(lut);
-}
-
-void usb_endpoint::completed_list_add(libusb_transfer *lut)
-{
-    _completed_list.push_back(lut);
-}
-
-
-/*
- * Free and completed lists don't have ordered content 
- * Pop transfers from the front as needed
- */
-libusb_transfer *usb_endpoint::free_list_get()
-{
+libusb_transfer *usb_endpoint::get_lut_with_wait(size_t timeout_ms){
+    boost::this_thread::disable_interruption di; //disable because the wait can throw
     libusb_transfer *lut;
-
-    if (_free_list.size() == 0) {
-        return NULL; 
-    }
-    else { 
-        lut = _free_list.front();
-        _free_list.pop_front();
-        return lut;
-    }
-}
-
-
-/*
- * Free and completed lists don't have ordered content 
- * Pop transfers from the front as needed
- */
-libusb_transfer *usb_endpoint::completed_list_get()
-{
-    libusb_transfer *lut;
-
-    if (_completed_list.empty()) {
-        return NULL;
-    }
-    else { 
-        lut = _completed_list.front();
-        _completed_list.pop_front();
-        return lut;
-    }
+    if (_completed_list->pop_with_timed_wait(
+        lut, boost::posix_time::milliseconds(timeout_ms)
+    )) return lut;
+    return NULL;
 }
 
-
-/*
- * Search and remove transfer from pending list
- * Assuming that the callbacks occur in order, the front element
- * should yield the correct transfer. If not, then something else
- * is going on. If no transfers match, then something went wrong.
- */
-bool usb_endpoint::pending_list_remove(libusb_transfer *lut)
-{
-    std::list<libusb_transfer*>::iterator iter;
-    for (iter = _pending_list.begin(); iter != _pending_list.end(); iter++) {
-        if (*iter == lut) { 
-            _pending_list.erase(iter);
-            return true;
-        }
-    }
-    return false;
-}
-
-
 /***********************************************************************
  * Managed buffers 
  **********************************************************************/
@@ -518,17 +293,15 @@ bool usb_endpoint::pending_list_remove(libusb_transfer *lut)
 class libusb_managed_recv_buffer_impl : public managed_recv_buffer {
 public:
     libusb_managed_recv_buffer_impl(libusb_transfer *lut,
-                                    usb_endpoint *endpoint)
+                                    usb_endpoint::sptr endpoint)
         : _buff(lut->buffer, lut->length)
     {
         _lut = lut;
         _endpoint = endpoint;
     }
 
-    ~libusb_managed_recv_buffer_impl()
-    {
-       if (!_endpoint->submit(_lut))
-           std::cerr << "USB: failed to submit IN transfer" << std::endl;
+    ~libusb_managed_recv_buffer_impl(void){
+        _endpoint->submit(_lut);
     }
 
 private:
@@ -538,7 +311,7 @@ private:
     }
 
     libusb_transfer *_lut;
-    usb_endpoint *_endpoint;
+    usb_endpoint::sptr _endpoint;
     const boost::asio::const_buffer _buff;
 };
 
@@ -554,7 +327,7 @@ private:
 class libusb_managed_send_buffer_impl : public managed_send_buffer {
 public:
     libusb_managed_send_buffer_impl(libusb_transfer *lut,
-                                    usb_endpoint *endpoint,
+                                    usb_endpoint::sptr endpoint,
                                     size_t buff_size)
         : _buff(lut->buffer, buff_size), _committed(false)
     {
@@ -562,8 +335,7 @@ public:
         _endpoint = endpoint;
     }
 
-    ~libusb_managed_send_buffer_impl()
-    {
+    ~libusb_managed_send_buffer_impl(void){
         if (!_committed) {
             _lut->length = 0;
             _lut->actual_length = 0;
@@ -583,12 +355,14 @@ public:
         _lut->length = num_bytes;
         _lut->actual_length = 0;
 
-        if (_endpoint->submit(_lut)) {
+        try{
+            _endpoint->submit(_lut);
             _committed = true;
             return num_bytes;
         }
-        else {
-            return 0;
+        catch(const std::exception &e){
+            std::cerr << "Error in commit: " << e.what() << std::endl;
+            return -1;
         }
     }
 
@@ -599,7 +373,7 @@ private:
     }
 
     libusb_transfer *_lut;
-    usb_endpoint *_endpoint;
+    usb_endpoint::sptr _endpoint;
     const boost::asio::mutable_buffer _buff;
     bool _committed;
 };
@@ -611,14 +385,9 @@ private:
 class libusb_zero_copy_impl : public usb_zero_copy
 {
 private:
-    usb_endpoint          *_rx_ep;
-    usb_endpoint          *_tx_ep;
+    usb_endpoint::sptr _rx_ep, _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;
 
     size_t _recv_buff_size;
     size_t _send_buff_size;
@@ -627,13 +396,11 @@ 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,
                           size_t send_buff_size);
-    
-    ~libusb_zero_copy_impl();
 
     managed_recv_buffer::sptr get_recv_buff(void);
     managed_send_buffer::sptr get_send_buff(void);
@@ -647,73 +414,43 @@ 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),
    _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 = usb_endpoint::sptr(new usb_endpoint(
+                              _handle,         // libusb device_handle
                               rx_endpoint,     // USB endpoint number
                               true,            // IN endpoint
                               _recv_buff_size, // buffer size per transfer 
-                              _num_frames);    // number of libusb transfers
+                              _num_frames      // number of libusb transfers
+    ));
 
-    _tx_ep = new usb_endpoint(_tx_dev_handle,  // libusb device_handle
-                              _tx_ctx,         // libusb context
+    _tx_ep = usb_endpoint::sptr(new usb_endpoint(
+                              _handle,         // libusb device_handle
                               tx_endpoint,     // USB endpoint number
                               false,           // OUT endpoint
                               _send_buff_size, // buffer size per transfer
-                              _num_frames);    // number of libusb transfers
+                              _num_frames      // number of libusb transfers
+    ));
 }
 
-
-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);
-}
-
-
 /*
  * Construct a managed receive buffer from a completed libusb transfer
  * (happy with buffer full of data) obtained from the receive endpoint.
  * Return empty pointer if no transfer is available (timeout or error).
  * \return pointer to a managed receive buffer 
  */
-managed_recv_buffer::sptr libusb_zero_copy_impl::get_recv_buff()
-{
-    libusb_transfer *lut = _rx_ep->get_completed_transfer();
+managed_recv_buffer::sptr libusb_zero_copy_impl::get_recv_buff(void){
+    libusb_transfer *lut = _rx_ep->get_lut_with_wait(/* TODO timeout API */);
     if (lut == NULL) {
         return managed_recv_buffer::sptr();
     }
@@ -731,9 +468,8 @@ managed_recv_buffer::sptr libusb_zero_copy_impl::get_recv_buff()
  * (timeout or error).
  * \return pointer to a managed send buffer 
  */
-managed_send_buffer::sptr libusb_zero_copy_impl::get_send_buff()
-{
-    libusb_transfer *lut = _tx_ep->get_free_transfer();
+managed_send_buffer::sptr libusb_zero_copy_impl::get_send_buff(void){
+    libusb_transfer *lut = _tx_ep->get_lut_with_wait(/* TODO timeout API */);
     if (lut == NULL) {
         return managed_send_buffer::sptr();
     }
@@ -756,12 +492,12 @@ 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, 
                                           block_size));
 }
-
-
-