Hi Rémi,
On Tuesday 31 July 2012 21:39:40 Rémi Denis-Courmont wrote:
Le mardi 31 juillet 2012 19:28:12 Laurent Pinchart, vous avez écrit :
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...
But what prevents you from using MMAP ?