Android uses uinput to simulate input devices

In google remote, the android receiver receives the ir code sent from the socket and then simulates the ir code and sends it to the system for processing. This is the principle of the google remote receiver.

How does the system simulate the input event?
Method 1: It is implemented through Instrumentation. sendKeyDownUpSync. It is simple to use, but the problem is that the event sent by sendKeyDownUpSync cannot be run
InterceptKeyBeforeDispatching will not work properly HOME, VOL...
Method 2: uinput bridging. The principle is to use the existing uinput driver of the kernel to send the input event through the kernel-driven uinput. kl and kcm are also easy to use;


After the comparison of method 2 is better, the test code of method 2 is given below...

1. main Function: setup_uinput_device registers the device and creates a thread VirtualInputDev_EventThread, which repeats keycode;

  int main(){printf("Enter process !!!! \n");    stVirtualInputDevData *pKpdData = (stVirtualInputDevData*) malloc(sizeof(stVirtualInputDevData));  pKpdData->min_keycode = umin_keycode;  pKpdData->max_keycode = umax_keycode;    if (setup_uinput_device(pKpdData) < 0) {        printf("Unable to find uInput device\n");        free(pKpdData);        return -1;    }    pthread_attr_t attr;    pthread_attr_init(&attr);    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);    if (0 != pthread_create(&keypad_EventThreadId, &attr, VirtualInputDev_EventThread, (void *)0)) {        printf("Create KeypadEventThread Failed!!\n");        exit(1);    }    // Coverity server need set to ignore this.    while (1) {        usleep(1000000);  // sleep 1 second    }    free(pKpdData);    pKpdData = 0;    // Destroy the device    ioctl(uinp_fd, UI_DEV_DESTROY);    close(uinp_fd);    return 0;}

2. setup_uinput_device function to complete device registration. You can see that the uinput node is opened directly and the name, verdor, product, and bustype of the virtual device are set,
Finally, register the device through ioctl (uinp_fd, UI_DEV_CREATE ).

   int setup_uinput_device(stVirtualInputDevData* mstVirtualInputDevData){    struct uinput_user_dev uinp; // uInput device structure    int i;    // Open the input device    uinp_fd = open("/dev/uinput", O_WRONLY | O_NDELAY);    if (uinp_fd == 0) {        printf("Unable to open /dev/uinput\n");        return -1;    }    // Intialize the uInput device to NULL    memset(&uinp, 0x00, sizeof(uinp));    strncpy(uinp.name, "virtualinputdev", sizeof(uinp.name)-1);    uinp.id.vendor = 0x1341;    uinp.id.product = 0x0001;    uinp.id.bustype = BUS_VIRTUAL;    // Keyboard    ioctl(uinp_fd, UI_SET_EVBIT, EV_KEY);    for (i = mstVirtualInputDevData->min_keycode; i < mstVirtualInputDevData->max_keycode; i++) {        ioctl(uinp_fd, UI_SET_KEYBIT, i);    }    // Create input device into input sub-system    if (write(uinp_fd, &uinp, sizeof(uinp)) != sizeof(uinp)) {        printf("First write returned fail.\n");        return -1;    }    if (ioctl(uinp_fd, UI_DEV_CREATE)) {        printf("ioctl UI_DEV_CREATE returned fail.\n");        return -1;    }    return 1;}

3. The thread VirtualInputDev_EventThread only resends the key, which is completed through write_event_to_device.

   static void* VirtualInputDev_EventThread(void *driver_data){    unsigned char u8Keycode,i=umin_keycode;    while (1) {        u8Keycode = 0xff;        /* sleep an interval time */        usleep(2000000);//sleep 5 s        /* fill event to uinput device. */        write_event_to_device(i++, 0);if(i==4){i = 0;}printf ("virtualinputdev thread ...\n");//i %= umax_keycode;    }    printf ("virtualinputdev thread died\n");    pthread_exit(0);    return 0;}

4. write_event_to_device writes the event to the uinput node.

  void write_event_to_device(unsigned char u8KeyCode, unsigned char u8Repeat){    struct input_event event; // Input device structure    struct timespec s;    s.tv_nsec = 5000000L;    s.tv_sec = 0;    memset(&event, 0x00, sizeof(event));    gettimeofday(&event.time, 0);    event.type = EV_KEY;    event.code = u8KeyCode;    event.value = 1;    write(uinp_fd, &event, sizeof(event));    memset(&event, 0x00, sizeof(event));    gettimeofday(&event.time, 0);    event.type = EV_KEY;    event.code = u8KeyCode;    event.value = 0;    write(uinp_fd, &event, sizeof(event));    memset(&event, 0x00, sizeof(event));    gettimeofday(&event.time, 0);    event.type = EV_SYN;    event.code = SYN_REPORT;    event.value = 0;    write(uinp_fd, &event, sizeof(event));}