参考了这里：http://thiemonge.org/getting-started-with-uinput

代码如下：

#include <linux/input.h>
#include <linux/uinput.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>

int reportkey(int fd, uint16_t type, uint16_t keycode, int32_t value)
{
	int ret;

	struct input_event ev;

	memset(&ev, 0, sizeof(struct input_event));

	ev.type = type;
	ev.code = keycode;
	ev.value = value;

	ret = write(fd, &ev, sizeof(struct input_event));
	if (ret < 0) {
		printf("report key error!\n");
		return ret;
	}

/*	printf("key is %d %d\n", keycode, value);*/

	return 0;
}

int main(void)
{
	struct uinput_user_dev uidev;

	int fd, ret;

	fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);

	if (fd < 0) {
		return fd;
	}

	ret = ioctl(fd, UI_SET_EVBIT, EV_KEY);
	ret = ioctl(fd, UI_SET_EVBIT, EV_SYN);

	ret = ioctl(fd, UI_SET_KEYBIT, KEY_D);

	memset(&uidev, 0, sizeof(struct uinput_user_dev));

	snprintf(uidev.name, UINPUT_MAX_NAME_SIZE, "uinput-sample");
	uidev.id.bustype = BUS_USB;
	uidev.id.vendor = 0x1234;
	uidev.id.product = 0xfedc;
	uidev.id.version = 1;

	ret = write(fd, &uidev, sizeof(struct uinput_user_dev));

	ret = ioctl(fd, UI_DEV_CREATE);
	if (ret < 0) {
		close(fd);
		return ret;
	}

	while (1) {
		reportkey(fd, EV_KEY, KEY_D, 1);
		reportkey(fd, EV_SYN, SYN_REPORT, 0);
		reportkey(fd, EV_KEY, KEY_D, 0);
		reportkey(fd, EV_SYN, SYN_REPORT, 0);
		sleep(1);
	}

	ioctl(fd, UI_DEV_DESTROY);

	close(fd);

	return 0;
}