adb devices获得的设备标识

在命令行执行adb devices，你会得到连接上的设备，结果里面有每个设备的标识(serial number)。在adb的其他命令中，你可以用adb –s 来指定用某一个设备来执行命令，但是每个设备的serial number都不一样，adb是如何得到的呢？查看adb的源码后，发现其获取serial number的代码如下：

 //D:/project/android/android-1.5/development/host/windows/usb/api/adb_interface.cpp
 bool AdbInterfaceObject::GetSerialNumber(void* buffer,
                                          unsigned long* buffer_char_size,
                                          bool ansi) {
   if (!IsOpened()) {
     SetLastError(ERROR_INVALID_HANDLE);
     return false;
   }
   // Open USB device for this intefface
   HANDLE usb_device_handle = CreateFile(interface_name().c_str(),
                                         GENERIC_READ,
                                         FILE_SHARE_READ | FILE_SHARE_WRITE,
                                         NULL,
                                         OPEN_EXISTING,
                                         0,
                                         NULL);
   if (INVALID_HANDLE_VALUE == usb_device_handle)
     return NULL;
   WCHAR serial_number[512];
   // Send IOCTL
   DWORD ret_bytes = 0;
   BOOL ret = DeviceIoControl(usb_device_handle,
                              ADB_IOCTL_GET_SERIAL_NUMBER,
                              NULL, 0,
                              serial_number, sizeof(serial_number),
                              &ret_bytes,
                              NULL);
   // Preserve error accross CloseHandle
   ULONG error = ret ? NO_ERROR : GetLastError();
   ::CloseHandle(usb_device_handle);
   if (NO_ERROR != error) {
     SetLastError(error);
     return false;
   }
   unsigned long str_len =
     static_cast(wcslen(serial_number) + 1);
   if ((NULL == buffer) || (*buffer_char_size < str_len)) {
     *buffer_char_size = str_len;
     SetLastError(ERROR_INSUFFICIENT_BUFFER);
     return false;
   }
   if (!ansi) {
     // If user asked for wide char name just return it
     wcscpy(reinterpret_cast(buffer), serial_number);
     return true;
   }
   // We need to convert name from wide char to ansi string
   int res = WideCharToMultiByte(CP_ACP,
                                 0,
                                 serial_number,
                                 static_cast(str_len),
                                 reinterpret_cast(buffer),
                                 static_cast(*buffer_char_size),
                                 NULL,
                                 NULL);
   return (res != 0);
 }

 

从上面的代码可以看到，adb是通过DeviceIoControl发送ADB_IOCTL_GET_SERIAL_NUMBER获取的，而上面CreateFile使用的interface_name是adb设备的全路径，格式如"////?//usb#vid_xxxx&pid_xxxx&mi_xx#123456789abcdef#{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}，创建adb设备的代码如下：

 //D:/project/android/android-1.5/development/host/windows/usb/api/adb_api.cpp
 ADBAPIHANDLE AdbCreateInterface(GUID class_id,
                                 unsigned short vendor_id,
                                 unsigned short product_id,
                                 unsigned char interface_id) {
   // Enumerate all active interfaces for the given class
   AdbEnumInterfaceArray interfaces;
   if (!EnumerateDeviceInterfaces(class_id,
                                  DIGCF_DEVICEINTERFACE | DIGCF_PRESENT,
                                  true,
                                  true,
                                  &interfaces)) {
     return NULL;
   }
   if (interfaces.empty()) {
     SetLastError(ERROR_DEVICE_NOT_AVAILABLE);
     return NULL;
   }
   // Now iterate over active interfaces looking for the name match.
   // The name is formatted as such:
   // "////?//usb#vid_xxxx&pid_xxxx&mi_xx#123456789abcdef#{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}"
   // where
   //    vid_xxxx is for the vendor id (xxxx are hex for the given vendor id),
   //    pid_xxxx is for the product id (xxxx are hex for the given product id)
   //    mi_xx is for the interface id  (xx are hex for the given interface id)
   // EnumerateDeviceInterfaces will guarantee that returned interface names
   // will have our class id at the end of the name (those last XXXes in the
   // format). So, we only need to match the beginning of the name
   wchar_t match_name[64];
   if (0xFF == interface_id) {
     // No interface id for the name.
     swprintf(match_name, L"////?//usb#vid_%04x&pid_%04x#",
              vendor_id, product_id);
   } else {
     // With interface id for the name.
     swprintf(match_name, L"////?//usb#vid_%04x&pid_%04x&mi_%02x#",
              vendor_id, product_id, interface_id);
   }
   size_t match_len = wcslen(match_name);
   for (AdbEnumInterfaceArray::iterator it = interfaces.begin();
        it != interfaces.end(); it++) {
     const AdbInstanceEnumEntry& next_interface = *it;
     if (0 == wcsnicmp(match_name,
                       next_interface.device_name().c_str(),
                       match_len)) {
       // Found requested interface among active interfaces.
       return AdbCreateInterfaceByName(next_interface.device_name().c_str());
     }
   }
   SetLastError(ERROR_DEVICE_NOT_AVAILABLE);
   return NULL;
 }

 

adb是每个1秒没有所有的usb设备（classid：{0xf72fe0d4, 0xcbcb, 0x407d, {0x88, 0x14, 0x9e, 0xd6, 0x73, 0xd0, 0xdd, 0x6b}}），所以插上usb后起码要1秒adb devices才能发现新设备。

 //D:/project/android/android-1.5/system/core/adb/usb_windows.c
 void* device_poll_thread(void* unused) {
   D("Created device thread/n");
   while(1) {
     find_devices();
     adb_sleep_ms(1000);
   }
   return NULL;
 }

 

如果你用windows监听usb设备的方式去监听adb设备，你可以在PDEV_BROADCAST_DEVICEINTERFACE结构体的dbcc_name字段获得GetSerialNumber函数所使用的interface_name。