Frame buffer Reading fails!!

Frame buffer Reading fails!!

[Abhilash]

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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" <abhilash@avenir.net>
Cc: "Linux Frame Buffer Device Development"
<linux-fbdev-devel@lists.sourceforge.net>
Sent: Friday, December 27, 2002 5:03 PM
Subject: Re: [Linux-fbdev-devel] Screen Capturing


> On Fri, 27 Dec 2002, Abhilash wrote:
> > I need to capture the screen .For that I use mirror driver in
Windows
for
> > 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
> > method?
> > In Xlib there are some functions to capture screen and also heard
abt
VESA
> > 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




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Re: Frame buffer Reading fails!!

[Antonino Daplas]

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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