gistfile1.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#define TRUE 1
#define FALSE 0

// Read framebuffer info into fix and var, return TRUE on success or FALSE on failure
int get_screen_info(int fb, struct fb_fix_screeninfo *fix, struct fb_var_screeninfo *var)
{
    int ior = ioctl(fb, FBIOGET_FSCREENINFO, fix);

    printf("being get info\n");

    if (ior == -1)
    {
        fprintf(stderr, "ERROR: Failed to get fixed screen info: %s\n", strerror(errno));
        return FALSE;
    }

    printf("got info\n");

    ior = ioctl(fb, FBIOGET_VSCREENINFO, var);

    if (ior == -1)
    {
        fprintf(stderr, "ERROR: Failed to get variable screen info: %s\n", strerror(errno));
        return FALSE;
    }

    printf("framebuffer id: %s\n", fix->id);
    printf("  mem start:    %x (%d)\n", fix->smem_start, fix->smem_start);
    printf("  mem length:   %x (%d)\n", fix->smem_len,   fix->smem_len);
    printf("  mmio start:   %x (%d)\n", fix->mmio_start, fix->mmio_start);
    printf("  mmio length:  %x (%d)\n", fix->mmio_len,   fix->mmio_len);
    printf("  line length:  %d\n", fix->line_length);
    printf("  type:         %d\n", fix->type);
    printf("  visual:       %d\n", fix->visual);
    printf("  accel:        %d\n", fix->accel);

    printf("  xres:         %d\n", var->xres);
    printf("  yres:         %d\n", var->yres);
    printf("  xres_virtual: %d\n", var->xres_virtual);
    printf("  yres_virtual: %d\n", var->yres_virtual);
    printf("  bits_pp:      %d\n", var->bits_per_pixel);
    //printf("  accel:        %d\n", fix->accel);
    //printf("  accel:        %d\n", fix->accel);
    //printf("  accel:        %d\n", fix->accel);
}


int main(int argc, char **argv)
{
    int fb = open("/dev/fb0", O_RDWR);

    if (fb == -1) 
    {
        fprintf(stderr, "Failed to open framebuffer\n");
        exit(1);
    }

    // Read out screen info (for framebuffer size etc)
    struct fb_fix_screeninfo fsi;
    struct fb_var_screeninfo vsi;

    if (!get_screen_info(fb, &fsi, &vsi))
        exit(1);

    char *fbmem = mmap(NULL, fsi.smem_len, PROT_READ|PROT_WRITE, MAP_SHARED, fb, 0);

    if (!fbmem)
    {
        fprintf(stderr, "ERROR: Failed to mmap framebuffer\n");
        exit(1);
    }

    int i;
    int z = 0;
    while (1)
    {
        z++;
        //for (i = 0; i < fsi.smem_len; i++) fbmem[i] = z;
        //for (i = 0; i < fsi.smem_len; i++) fbmem[i] = z*z;
        //for (i = 0; i < fsi.smem_len; i++) fbmem[i] = i*z+(i%200);
        //for (i = 0; i < fsi.smem_len; i++) fbmem[i] = i*i*z+(i%3000);
        for (i = 0; i < fsi.smem_len; i++) fbmem[i] = i*i*z;
        //for (i = 0; i < fsi.smem_len; i++) fbmem[i] = i+i*z;
        //for (i = 0; i < fsi.smem_len; i++) fbmem[i] = i+i*z+z;
    }
}