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Commit 3f60a968 authored by Josh Gao's avatar Josh Gao
Browse files

adb: libusb: wait for devices to become accessible. 

Android's host linux libusb uses netlink instead of udev for device
hotplug notification, which means we can get hotplug notifications
before udev has updated ownership/perms on the device.

When detecting a new device, poll the device file for a while until we
can access it, before trying to open it.

Bug: http://b/38170349
Test: manually incrased timeout and chmodded a device betwen 0 and 664
Change-Id: I3c714f630940df02b407442592301e2bbb3d9653
parent 6da1cd49

adb/client/usb_libusb.cpp

+47 −4
Original line number Diff line number Diff line
@@ -172,6 +172,17 @@ static std::string get_device_serial_path(libusb_device* device) { 
    path += "/serial";

    return path;

}



static std::string get_device_dev_path(libusb_device* device) {

    uint8_t ports[7];

    int port_count = libusb_get_port_numbers(device, ports, 7);

    if (port_count < 0) return "";

    return StringPrintf("/dev/bus/usb/%03u/%03u", libusb_get_bus_number(device), ports[0]);

}



static bool is_device_accessible(libusb_device* device) {

    return access(get_device_dev_path(device).c_str(), R_OK | W_OK) == 0;

}

#endif



static bool endpoint_is_output(uint8_t endpoint) {
@@ -368,11 +379,38 @@ static void process_device(libusb_device* device) { 
    }



    register_usb_transport(usb_handle_raw, device_serial.c_str(), device_address.c_str(), writable);



    LOG(INFO) << "registered new usb device '" << device_serial << "'";

}



static void remove_device(libusb_device* device) {

static std::atomic<int> connecting_devices(0);



static void device_connected(libusb_device* device) {

#if defined(__linux__)

    // Android's host linux libusb uses netlink instead of udev for device hotplug notification,

    // which means we can get hotplug notifications before udev has updated ownership/perms on the

    // device. Since we're not going to be able to link against the system's libudev any time soon,

    // hack around this by checking for accessibility in a loop.

    ++connecting_devices;

    auto thread = std::thread([device]() {

        std::string device_path = get_device_dev_path(device);

        auto start = std::chrono::steady_clock::now();

        while (std::chrono::steady_clock::now() - start < 500ms) {

            if (is_device_accessible(device)) {

                break;

            }

            std::this_thread::sleep_for(10ms);

        }



        process_device(device);

        --connecting_devices;

    });

    thread.detach();

#else

    process_device(device);

#endif

}



static void device_disconnected(libusb_device* device) {

    std::string device_address = get_device_address(device);



    LOG(INFO) << "device disconnected: " << device_address;
@@ -390,9 +428,9 @@ static void remove_device(libusb_device* device) { 
static int hotplug_callback(libusb_context*, libusb_device* device, libusb_hotplug_event event,

                            void*) {

    if (event == LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED) {

        process_device(device);

        device_connected(device);

    } else if (event == LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT) {

        remove_device(device);

        device_disconnected(device);

    }

    return 0;

}
@@ -415,6 +453,11 @@ void usb_init() { 
        LOG(FATAL) << "failed to register libusb hotplug callback";

    }



    // Wait for all of the connecting devices to finish.

    while (connecting_devices != 0) {

        std::this_thread::sleep_for(10ms);

    }



    adb_notify_device_scan_complete();



    // Spawn a thread for libusb_handle_events.