Messages in this thread | | | From | Laurent Pinchart <> | Subject | Re: How to efficiently handle DMA and cache on ARMv7 ? (was " Is get user pages() enough to prevent pages from being swapped out ?") | Date | Fri, 7 Aug 2009 12:13:48 +0200 |
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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
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