Hi Rémi, On Tuesday 31 July 2012 16:39:00 Rémi Denis-Courmont wrote: > 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. Could you please share your use case(s) with us ? > 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. -- 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
