/*
 * From "Testing the Linux Framebuffer"
 * http://doc.trolltech.com/4.2/qtopiacore-testingframebuffer.html
 *
 * "To test that the Linux framebuffer is set up correctly, and that the device
 * permissions are correct, use the program below which opens the frame buffer
 * and draws a gradient-filled red square."
 *
 * Use this after making changes to the framebuffer driver. See
 * http://mrobefan.devjavu.com/projects/mrobefan/wiki/Fbtest.
 */
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <stdlib.h>
#include <sys/ioctl.h>

int main(int argc, char* argv[])
{
    int fbfd = 0;
    struct fb_var_screeninfo vinfo;
	char *device="/dev/fb0";
	
	if(argc>1)
	{
		device=argv[1];
	}
	
    // Open the file for reading and writing
    fbfd = open(device, O_RDWR);
    if (!fbfd) 
    {
        printf("Error: cannot open framebuffer device.\n");
        exit(1);
    }
    printf("The framebuffer device was opened successfully.\n");

    // Get variable screen information
    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) 
    {
        printf("Error reading variable information.\n");
        exit(3);
    }

    vinfo.yres_virtual=482;
	int err = ioctl(fbfd, FBIOPUT_VSCREENINFO, &vinfo);
	if (err)
    {
    	printf("***ERROR*** File %s, Line %i, errorcode:%i\n", __FILE__, __LINE__,err);
        printf("Warning: FBIOPUT_VSCREENINFO Failed, could not set new virtual yres.");
        return -1;
    }

	printf("%dx%d, virt: %d\n", vinfo.xres, vinfo.yres, vinfo.yres_virtual);

	vinfo.yoffset = 2;
	err = ioctl(fbfd,FBIOPAN_DISPLAY, &vinfo);
	if(err)
	{
		printf("***ERROR*** File %s, Line %i, errorcode:%i\n", __FILE__, __LINE__,err);
		printf("Setting PAN failed (ioctl:FBIOPAN_DISPLAY)\n");
		return -1;
	}

    close(fbfd);
    return 0;
}