framebuffer test

fb_test.c

#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/fb.h>
#include <sys/mman.h>

#include <stdio.h>
#include <stdint.h>

static struct fb_var_screeninfo sinfo;
static struct fb_fix_screeninfo fix_info;

int
main (void)
{
    int fd;
    int err;

    fd = open ("/dev/fb0", O_RDWR);

    if (fd == -1)
    {
        printf ("/dev/fb0\n");
        return 1;
    }

    if (ioctl (fd, FBIOGET_FSCREENINFO, &fix_info))
    {
        printf ("fix screen\n");
        goto leave;
    }
    
    if (ioctl (fd, FBIOGET_VSCREENINFO, &sinfo))
    {
        printf ("var screen\n");
        goto leave;
    }

    printf ("x=%d\n", sinfo.xres);
    printf ("y=%d\n", sinfo.yres);
    printf ("mem_len=%d\n", fix_info.smem_len);

    {
        uint8_t *fbmem;

        /* map the framebuffer */
        fbmem = mmap (NULL, fix_info.smem_len, PROT_WRITE, MAP_SHARED, fd, 0);
        if (fbmem == MAP_FAILED)
        {
            printf ("mmap\n");
            goto leave;
        }

        {
            unsigned int i;
            for (i = 0; i < fix_info.smem_len / 4; i++)
                ((uint32_t*) fbmem)[i] = 0x80008000;
        }
    }

leave:
    close (fd);

    return 0;
}