On Thursday 06 August 2009 20:46:14 David Xiao wrote: [snip] > Another approach is working from a different direction: the kernel > allocates the non-cached buffer and then mmap() into user space. I have > done that in similar situation to try to achieve "zero-copy". That's what most drivers do. While it's probably the easiest solution in many cases, it will sometimes introduce additional memcpy() operations that I'd like to avoid. 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. Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
