RE: Adding an fb_sync() operation to fb_ops

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


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