#include <stdio.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <sys/mman.h>

#include <linux/fb.h>

#define FB_DEV "/dev/fb0"       

#define SCREEN_RED   0xFF0000

#define SCREEN_GREEN 0x00FF00

#define SCREEN_BLUE  0x0000FF

void draw_point(unsigned int x,unsigned int y,unsigned int color);

void draw_line(unsigned int x0,unsigned int y0,unsigned int x1,unsigned int y1,unsigned int color);

static struct fb_var_screeninfo varScreenInfo = {};

static struct fb_fix_screeninfo fixScreenInfo = {};

static unsigned int *pfb_buffer = NULL;

int main(void)

{

    int ret = -;

    int fd = -;

    fd = open(FB_DEV, O_RDWR);

    if(fd < )

    {

        perror("open");

        close(fd);

        return -;

    }

    ret = ioctl(fd, FBIOGET_FSCREENINFO,&fixScreenInfo);

    if(ret < )

    {

        perror("ioctl");

        close(fd);

        return ret;

    }

    ret = ioctl(fd, FBIOGET_VSCREENINFO,&varScreenInfo);

    if(ret < )

    {

        perror("ioctl");

        close(fd);

        return ret;

    }

    printf("smem_len = %d\n",fixScreenInfo.smem_len);

    printf("xres         = %d;  yres         = %d\n",varScreenInfo.xres,varScreenInfo.yres);

    printf("xres_virtual = %d;  yres_virtual = %d\n",varScreenInfo.xres_virtual,varScreenInfo.yres_virtual);

    pfb_buffer = mmap(NULL, fixScreenInfo.smem_len, PROT_READ|PROT_WRITE, MAP_SHARED,fd,);

    printf("pfb_buffer = %p\n",pfb_buffer);

    draw_line(,,,,SCREEN_RED);

    close(fd);

    return ;

}

void draw_point(unsigned int x,unsigned int y,unsigned int color)

{

    x %=varScreenInfo.xres_virtual;

    y %=varScreenInfo.yres_virtual;

    // printf("x = %d  y = %d   %p\n",x,y,(pfb_buffer + x + (y*varScreenInfo.xres_virtual)));

    *(pfb_buffer + x + y*varScreenInfo.xres_virtual) = color;

}

void draw_line(unsigned int x0,unsigned int y0,unsigned int x1,unsigned int y1,unsigned int color)

{

    unsigned int x=,y=;

    float setp = (y1-y0)/(float)(x1-x0);

    for(x=x0,y=y0;x<x1;x++)

    {

        draw_point(x,y,color);

        y = y0+setp*(x-x0)        ;

    }

}