Frame buffer Reading fails!!

Hello,

As u suggested I tried following code in RedHat7.1.
But it shows

 "The framebuffer device was opened successfully."
 "Error reading fixed information."

What could be the problem?
I am new to this.

Thank you,
Abhilash.


#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);
    }
}

----- Original Message -----
From: "Geert Uytterhoeven" <geert@linux-m68k.org>
To: "Abhilash" <redacted>
Cc: "Linux Frame Buffer Device Development"
[off-list ref]
Sent: Friday, December 27, 2002 5:03 PM
Subject: Re: [Linux-fbdev-devel] Screen Capturing

On Fri, 27 Dec 2002, Abhilash wrote:

quoted

I need to capture the screen .For that I use mirror driver in

Windows
for

quoted

capturing screen.
ie, its basically overloading the driver functions.

So in case of Linux, is there any method like this or which is the

best

quoted

method?
In Xlib there are some functions to capture screen and also heard

abt
VESA

quoted

which is better?

If you are using a frame buffer device, you can capture the contents

of

/dev/fb*. Either read from /dev/fb*, or mmap() it. The data you

receive
are in

the native format of the graphics chip. For CLUT modes, you have to

use an

ioctl() to get the colormap.

Gr{oetje,eeting}s,

Geert

On Fri, 2003-01-03 at 23:48, Abhilash wrote:

Hello,

As u suggested I tried following code in RedHat7.1.
But it shows

 "The framebuffer device was opened successfully."
 "Error reading fixed information."

What could be the problem?
I am new to this.

Try doing it again as root.  /dev/fbX is most probably owned by root (as
it should be).

If it still doesn't work, do a  

cat /dev/urandom > /dev/fb0 

to check if /dev/fb0 is valid.  BTW, what fb driver are you using?

Tony





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