1 // Copyright 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "chrome/browser/usb/usb_context.h" 6 7 #include "base/logging.h" 8 #include "base/synchronization/waitable_event.h" 9 #include "base/threading/platform_thread.h" 10 #include "content/public/browser/browser_thread.h" 11 #include "third_party/libusb/src/libusb/interrupt.h" 12 #include "third_party/libusb/src/libusb/libusb.h" 13 14 // The UsbEventHandler works around a design flaw in the libusb interface. There 15 // is currently no way to signal to libusb that any caller into one of the event 16 // handler calls should return without handling any events. 17 class UsbContext::UsbEventHandler : public base::PlatformThread::Delegate { 18 public: 19 explicit UsbEventHandler(libusb_context* context); 20 virtual ~UsbEventHandler(); 21 22 // base::PlatformThread::Delegate 23 virtual void ThreadMain() OVERRIDE; 24 25 private: 26 volatile bool running_; 27 libusb_context* context_; 28 base::PlatformThreadHandle thread_handle_; 29 base::WaitableEvent start_polling_; 30 DISALLOW_COPY_AND_ASSIGN(UsbEventHandler); 31 }; 32 33 UsbContext::UsbEventHandler::UsbEventHandler(libusb_context* context) 34 : running_(true), 35 context_(context), 36 thread_handle_(0), 37 start_polling_(false, false) { 38 bool success = base::PlatformThread::Create(0, this, &thread_handle_); 39 DCHECK(success) << "Failed to create USB IO handling thread."; 40 start_polling_.Wait(); 41 } 42 43 UsbContext::UsbEventHandler::~UsbEventHandler() { 44 running_ = false; 45 // Spreading running_ to the UsbEventHandler thread. 46 base::subtle::MemoryBarrier(); 47 libusb_interrupt_handle_event(context_); 48 base::PlatformThread::Join(thread_handle_); 49 } 50 51 void UsbContext::UsbEventHandler::ThreadMain() { 52 base::PlatformThread::SetName("UsbEventHandler"); 53 VLOG(1) << "UsbEventHandler started."; 54 if (running_) { 55 start_polling_.Signal(); 56 libusb_handle_events(context_); 57 } 58 while (running_) 59 libusb_handle_events(context_); 60 VLOG(1) << "UsbEventHandler shutting down."; 61 } 62 63 UsbContext::UsbContext() : context_(NULL) { 64 DCHECK(thread_checker_.CalledOnValidThread()); 65 CHECK_EQ(0, libusb_init(&context_)) << "Cannot initialize libusb"; 66 event_handler_ = new UsbEventHandler(context_); 67 } 68 69 UsbContext::~UsbContext() { 70 // destruction of UsbEventHandler is a blocking operation. 71 DCHECK(thread_checker_.CalledOnValidThread()); 72 delete event_handler_; 73 event_handler_ = NULL; 74 libusb_exit(context_); 75 } 76
