Le mardi 31 juillet 2012 14:56:14 Laurent Pinchart, vous avez écrit : > > For that matter, wouldn't it be useful to support exporting a userptr > > buffer at some point in the future? > > Shouldn't USERPTR usage be discouraged once we get dma-buf support ? USERPTR, where available, is currently the only way to perform zero-copy from kernel to userspace. READWRITE does not support zero-copy at all. MMAP only supports zero-copy if userspace knows a boundary on the number of concurrent buffers *and* the device can deal with that number of buffers; in general, MMAP requires memory copying. I am not sure DMABUF even supports transmitting data efficiently to userspace. In my understanding, it's meant for transmitting data between DSP's bypassing userspace entirely, in other words the exact opposite of what USERBUF does. -- Rémi Denis-Courmont http://www.remlab.net/ http://fi.linkedin.com/in/remidenis -- 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
