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.
5 #include "chrome/browser/usb/usb_context.h"
7 #include "base/logging.h"
8 #include "base/synchronization/waitable_event.h"
9 #include "base/threading/platform_thread.h"
10 #include "third_party/libusb/src/libusb/interrupt.h"
11 #include "third_party/libusb/src/libusb/libusb.h"
13 // The UsbEventHandler works around a design flaw in the libusb interface. There
14 // is currently no way to signal to libusb that any caller into one of the event
15 // handler calls should return without handling any events.
16 class UsbContext::UsbEventHandler : public base::PlatformThread::Delegate {
18 explicit UsbEventHandler(libusb_context* context);
19 virtual ~UsbEventHandler();
21 // base::PlatformThread::Delegate
22 virtual void ThreadMain() OVERRIDE;
25 volatile bool running_;
26 libusb_context* context_;
27 base::PlatformThreadHandle thread_handle_;
28 base::WaitableEvent start_polling_;
29 DISALLOW_COPY_AND_ASSIGN(UsbEventHandler);
32 UsbContext::UsbEventHandler::UsbEventHandler(libusb_context* context)
36 start_polling_(false, false) {
37 bool success = base::PlatformThread::Create(0, this, &thread_handle_);
38 DCHECK(success) << "Failed to create USB IO handling thread.";
39 start_polling_.Wait();
42 UsbContext::UsbEventHandler::~UsbEventHandler() {
44 // Spreading running_ to the UsbEventHandler thread.
45 base::subtle::MemoryBarrier();
46 libusb_interrupt_handle_event(context_);
47 base::PlatformThread::Join(thread_handle_);
50 void UsbContext::UsbEventHandler::ThreadMain() {
51 base::PlatformThread::SetName("UsbEventHandler");
52 VLOG(1) << "UsbEventHandler started.";
54 start_polling_.Signal();
55 libusb_handle_events(context_);
58 libusb_handle_events(context_);
59 VLOG(1) << "UsbEventHandler shutting down.";
62 UsbContext::UsbContext(PlatformUsbContext context) : context_(context) {
63 DCHECK(thread_checker_.CalledOnValidThread());
64 event_handler_ = new UsbEventHandler(context_);
67 UsbContext::~UsbContext() {
68 // destruction of UsbEventHandler is a blocking operation.
69 DCHECK(thread_checker_.CalledOnValidThread());
70 delete event_handler_;
71 event_handler_ = NULL;
72 libusb_exit(context_);