Le mardi 31 juillet 2012 19:28:12 Laurent Pinchart, vous avez écrit :
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 want to receive the video buffers in user space for processing. Typically "processing" is software encoding or conversion. That's what virtually any V4L application does on the desktop...