Re: How to efficiently handle DMA and cache on ARMv7 ? (was " Is get_user_pages() enough to prevent pages from being swapped out ?")

[Laurent Pinchart]

On Friday 07 August 2009 10:12:23 Matthieu CASTET wrote:
> Laurent Pinchart a écrit :
> > On Thursday 06 August 2009 20:46:14 David Xiao wrote:
> >
> > Think about the simple following use case. An application wants to
> > display video it acquires from the device to the screen using Xv. The
> > video buffer is allocated by Xv. Using the v4l2 user pointer streaming
> > method, the device can DMA directly to the Xv buffer. Using
> > driver-allocated buffers, a memcpy() is required between the v4l2 buffer
> > and the Xv buffer.
>
> v4l2 got an API (overlay IRRC) that allow drivers to write directly in
> framebuffer memory.

That's right, but I was mostly using this as an example.

> BTW Xv buffer is not always in video memory and the X driver can do a
> memcpy.

Still, one less memcpy is better :-)

Regards,

Laurent Pinchart

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/