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

[Matthieu CASTET <matthieu.castet@parrot.com>]

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


Matthieu