hi all..
i have enabled framebuffer in the config file
of kernel and then recompiled it..
i have even set the parameters for VGA in grub.conf
but when i try running sample appilications the screen
just goes blank!!!!
i have tried running this simple test program
as follows
but even this doesnt seem to be working!!!
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
int main()
{
int fbfd = 0;
struct fb_var_screeninfo vinfo;
struct fb_fix_screeninfo finfo;
long int screensize = 0;
char *fbp = 0;
int x = 0, y = 0;
long int location = 0;
// Open the file for reading and writing
fbfd = open("/dev/fb0", O_RDWR);
if (!fbfd) {
printf("Error: cannot open framebuffer
device.\n");
exit(1);
}
printf("The framebuffer device was opened
successfully.\n");
// Get fixed screen information
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
printf("Error reading fixed information.\n");
exit(2);
}
// Get variable screen information
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
printf("Error reading variable
information.\n");
exit(3);
}
printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres,
vinfo.bits_per_pixel );
// Figure out the size of the screen in bytes
screensize = vinfo.xres * vinfo.yres *
vinfo.bits_per_pixel / 8;
// Map the device to memory
fbp = (char *)mmap(0, screensize, PROT_READ |
PROT_WRITE, MAP_SHARED,
fbfd, 0);
if ((int)fbp == -1) {
printf("Error: failed to map framebuffer
device to memory.\n");
exit(4);
}
printf("The framebuffer device was mapped to
memory successfully.\n");
x = 100; y = 100; // Where we are going to
put the pixel
// Figure out where in memory to put the pixel
for ( y = 100; y < 300; y++ )
for ( x = 100; x < 300; x++ ) {
location = (x+vinfo.xoffset) *
(vinfo.bits_per_pixel/8) +
(y+vinfo.yoffset) *
finfo.line_length;
if ( vinfo.bits_per_pixel == 32 ) {
*(fbp + location) = 100; //
Some blue
*(fbp + location + 1) = 15+(x-100)/2;
// A little green
*(fbp + location + 2) = 200-(y-100)/5;
// A lot of red
*(fbp + location + 3) = 0; // No
transparency
} else { //assume 16bpp
int b = 10;
int g = (x-100)/6; // A little
green
int r = 31-(y-100)/16; // A lot of
red
unsigned short int t = r<<11 | g << 5
| b;
*((unsigned short int*)(fbp +
location)) = t;
}
}
munmap(fbp, screensize);
close(fbfd);
return 0;
}
i m getting the following error
Error: failed to map framebuffer device to memory
thanks all!!!
regards
manu
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