RE: [Linux-fbdev-devel] Adding an fb_sync() operation to fb_ops

[Antonino D. <ad...@po...>]

On Mon, 2002-06-03 at 23:49, Sottek, Matthew J wrote:
> 
> So here is the obvious problem case.
> 
> Application mmap's the framebuffer.
> Application Draws some pixels into the framebuffer.
> Application issues an ioctl that would lead to a blit, the command is put
>  in a ring buffer but hasn't happened yet.
> The application draws some more pixels (via the mmap) in a region that
>  intersects the previously blitted region.
> The hardware gets around to the blit command and overwrites the pixels you
>   just put in the frambuffer.
> 
> 
And it does not have to happen outside the kernel.  Within the kernel
too.  For instance, a particular accelerator may only support fillrect
and copyarea, but not imageblit (neofb).  It has no choice but to mix in
cfb_imageblit and the sync problem will arise unless the accelerator
forces a sync -- which neofb does by the way.
  
Tony