[PATCHv2 3/9] v4l: add buffer exporting via dmabuf

[Laurent Pinchart]

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 ?

-- 
Regards,

Laurent Pinchart