VSYNC test for Allwinner A10 display controller

teardemo.c

#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <assert.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <sys/ioctl.h>
#include <linux/fb.h>

/* fill left half of the framebuffer with white, and right with black */
void fill_framebuffer(char *buf, int pitch, int height, int bw_split_pos)
{
    while (height--) {
        memset(buf, 0xFF, bw_split_pos);
        memset(buf + bw_split_pos, 0x00, pitch - bw_split_pos);
        buf += pitch;
    }
}

int main(int argc, char *argv[])
{
    struct fb_fix_screeninfo finfo;
    char *buf = 0;
    int fd, pos = 0;
    if ((fd = open("/dev/fb0", O_RDWR)) < 0) {
        printf("can't open /dev/fb0");
        return 1;
    }
    ioctl(fd, FBIOGET_FSCREENINFO, &finfo);
    buf = mmap(0, finfo.smem_len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    while (1) {
        pos = (pos + 128) % (finfo.line_length * 2);
        ioctl(fd, FBIO_WAITFORVSYNC, 0);
        fill_framebuffer(buf, finfo.line_length,
                         finfo.smem_len / finfo.line_length,
                         pos < finfo.line_length ?
                         pos : 2 * finfo.line_length - pos);
    }
    return 0;
}