linux uinput:简单示例? [英] linux uinput: simple example?

问题描述

我在使用uinput来获取双方的代码时遇到了一些问题.

I'm having some problems getting both sides of code using uinput working.

基于 uinput入门:用户级输入子系统 ^{[死链接； 已存档]} 我整理了以下 writer (减去错误处理):

Based on Getting started with uinput: the user level input subsystem^{[dead link; archived]} I put together the following writer (minus error handling):

int main(int ac, char **av)
{
    int fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    int ret = ioctl(fd, UI_SET_EVBIT, EV_ABS);
    ret = ioctl(fd, UI_SET_ABSBIT, ABS_X);

    struct uinput_user_dev uidev = {0};
    snprintf(uidev.name, UINPUT_MAX_NAME_SIZE, "uinput-rotary");
    uidev.absmin[ABS_X] = 0;
    uidev.absmax[ABS_X] = 255;
    ret = write(fd, &uidev, sizeof(uidev));
    ret = ioctl(fd, UI_DEV_CREATE);

    struct input_event ev = {0};
    ev.type = EV_ABS;
    ev.code = ABS_X;
    ev.value = 42;

    ret = write(fd, &ev, sizeof(ev));

    getchar();

    ret = ioctl(fd, UI_DEV_DESTROY);
    return EXIT_SUCCESS;
}

这似乎可行，至少似乎已经编写了完整的input_event结构.

That seems to work, at least the full input_event structure seems to be written.

然后，我写出最幼稚的 reader 我可以想到的事件:

I then wrote the most naive reader of events I could come up with:

int main(int ac, char **av)
{
    int fd = open(av[1], O_RDONLY);

    char name[256] = "unknown";
    ioctl(fd, EVIOCGNAME(sizeof(name)), name);
    printf("reading from %s\n", name);

    struct input_event ev = {0};
    int ret = read(fd, &ev, sizeof(ev));
    printf("Read an event! %i\n", ret);
    printf("ev.time.tv_sec: %li\n", ev.time.tv_sec);
    printf("ev.time.tv_usec: %li\n", ev.time.tv_usec);
    printf("ev.type: %hi\n", ev.type);
    printf("ev.code: %hi\n", ev.code);
    printf("ev.value: %li\n", ev.value);

    return EXIT_SUCCESS;
}

不幸的是，读者方面根本无法工作.每次只能读取8个字节，这几乎不是完整的input_event结构.

Unfortunately the reader side doesn't work at all; only manages to read 8 bytes each time, which isn't nearly a full input_event structure.

我犯了什么愚蠢的错误?

What silly mistake am I making?

推荐答案

您还应该在实际事件之后编写一个同步事件.在您的编写方代码中:

You should also be writing a sync event after the actual event. In your writer side code:

struct input_event ev = {0};
ev.type = EV_ABS;
ev.code = ABS_X;
ev.value = 42;

usleep(1500);

memset(&ev, 0, sizeof(ev));
ev.type = EV_SYN;
ev.code = 0;
ev.value = 0;

ret = write(fd, &ev, sizeof(ev));

getchar();

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