Re: Gives Bus error in memcpy() in coping /dev/fb0 to a file.

["Antonino A. Daplas" <adaplas@gmail.com>]

On Fri, 2007-03-09 at 14:39 +0530, Vishal Soni wrote:
> > > > I don't think vfb's framebuffer can be mmapped.  It's fixable, but
> > > > nobody seems to have a need for it,  yet.
> > > >
> > > > Tony
> > >
> > > fb is getting successfully mapped.. its just that memcpy gives bus error
> > > when i try to copy the mapped memory of framebuffer device to a "mapped
> > > file,"
> > >
> > > Well, I am able to get the ball rolling by writing the mapped framebuffer
> > > onto the file by using write system call
> >
> > Unless you modified vfb yourself, it's not possible because
> > fix->smem_start is not set all (it's pointing to NULL). What's actually
> > being mmapped is physical addres 0UL.
> what i wanted to do......as i wrote in my very first mail........ i
> have got that, now i am able to capture the snapshot using c program
> and the results are output on my screen....
>       printf("frame bufffer mapped  @ %p\n", src);
>       for(i = 0; i < vinfo.xres*vinfo.yres*vinfo.bits_per_pixel/8; i++)
>                 *src++ = 0xBB;
> 
> Framebuffer is getting mapped... by mmap system call
>   // Map the device to memory
>         src = (char *)mmap(0, screensize, PROT_READ|PROT_WRITE,
> MAP_SHARED, fdin, 0);
>         if ((int)src == -1) {
>                 printf("Error: failed to map framebuffer device to memory.\n");
>                 return -1;
>         }
> 
> and therefore  physical addres 0UL is not what is mapped.....its the
> framebuffer.
> doubt in my last mail was w.r.t memcpy().

Well you had me confused, you mentioned virtual framebuffer, but I think
you are actually using the VESA framebuffer.

Anyway, the bus error is because the source file is truncated to zero
size. Try instead to open a file whose size is >= screensize.

Tony



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