On Sun, 18 Jun 2000, Jeff Garzik wrote:
> Gerd Knorr wrote:
> > The v4l2 capture interface should use kiobufs instead of let the
> > applications mmap() kernel-space capture buffers. Unfortunaly drivers
> > will have to support both kiobufs and mmap to maintain v4l1 backward
> > compatibility.
>
> Why?
I don't like the need to use unswapable kernel memory for capuring. It
also allows to capturing to any memory area, including shared memory
segments (MIT-SHM...).
> Some frame grabber can't retain performance if they are constantly
> changing the capture buffer address ...
I think this is just a question of the interface design. If the
application has to register the memory it wants to use for capturing
(instead of mapping the buffers like one would do with the current v4l2
interface) the driver can decide to either lock down all memory between
VIDIOC_STREAMON and VIDIOC_STREAMOFF ioctls or just lock down the
individual buffers while capturing the frames.
Gerd
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