[st-ericsson] v4l2 vs omx for camera

[Robert Fekete]

On 28 February 2011 11:33, Laurent Pinchart <
laurent.pinchart at ideasonboard.com> wrote:

> On Monday 28 February 2011 11:21:52 Hans Verkuil wrote:
> > On Monday, February 28, 2011 11:11:47 Laurent Pinchart wrote:
> > > On Saturday 26 February 2011 13:12:42 Hans Verkuil wrote:
> > > > On Friday, February 25, 2011 18:22:51 Linus Walleij wrote:
> > > > > 2011/2/24 Edward Hervey <bilboed at gmail.com>:
> > > > > >  What *needs* to be solved is an API for data allocation/passing
> at
> > > > > > the kernel level which v4l2,omx,X,GL,vdpau,vaapi,... can use and
> > > > > > that userspace (like GStreamer) can pass around, monitor and know
> > > > > > about.
> > > > >
> > > > > I think the patches sent out from ST-Ericsson's Johan Mossberg to
> > > > > linux-mm for "HWMEM" (hardware memory) deals exactly with buffer
> > > > > passing, pinning of buffers and so on. The CMA (Contigous Memory
> > > > > Allocator) has been slightly modified to fit hand-in-glove with
> > > > > HWMEM, so CMA provides buffers, HWMEM pass them around.
> > > > >
> > > > > Johan, when you re-spin the HWMEM patchset, can you include
> > > > > linaro-dev and linux-media in the CC?
>

Yepp..Johan will do that (his mail is fubar at the moment so I will answer
instead :-) )


> > > >
> > > > Yes, please. This sounds promising and we at linux-media would very
> > > > much like to take a look at this. I hope that the CMA + HWMEM
> > > > combination is exactly what we need.
> > >
> > > Once again let me restate what I've been telling for some time: CMA
> must
> > > be *optional*. Not all hardware need contiguous memory. I'll have a
> look
> > > at the next HWMEM version.
>

hwmem API has Scattered memory support as well (not implemented yet though)


> >
> > Yes, it is optional when you look at specific hardware. On a kernel level
> > however it is functionality that is required in order to support all the
> > hardware. There is little point in solving one issue and not the other.
>
> I agree. What I meant is that we need to make sure there's no HWMEM -> CMA
> dependency.
>
>
HWMEM has no CMA dependency, although hwmem is easily adapted ontop of
CMA(once the speculative prefetch stuff in ARM arch is resolved)


BR
/Robert F

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