Re: [GIT PATCH FOR 2.6.40] uvcvideo patches

[Arnd Bergmann <arnd@arndb.de>]

On Thursday 26 May 2011, Laurent Pinchart wrote:
> On Thursday 26 May 2011 01:50:07 Mauro Carvalho Chehab wrote:
> > Em 25-05-2011 20:43, Laurent Pinchart escreveu:
> > > Issues arise when devices have floating point registers. And yes, that
> > > happens, I've learnt today about an I2C sensor with floating point
> > > registers (in this specific case it should probably be put in the broken
> > > design category, but it exists :-)).
> > 
> > Huh! Yeah, an I2C sensor with FP registers sound weird. We need more
> > details in order to address those.
> 
> Fortunately for the sensor I'm talking about most of those registers are read-
> only and contain large values that can be handled as integers, so all we need 
> to do is convert the 32-bit IEEE float value into an integer. Other hardware 
> might require more complex FP handling.

As an additional remark here, most architectures can handle float in the
kernel in some way, but they all do it differently, so it's basically
impossible to do in a cross-architecture device driver.
 
> > I'm all about showing the industry in with direction we would like it to
> > go. We want that all Linux-supported architectures/sub-architectures
> > support inter-core communications in kernelspace, in a more efficient way
> > that it would happen if such communication would happen in userspace.
> 
> I agree with that. My concern is about things like
> 
> "Standardizing on the OpenMax media libraries and the GStreamer framework is 
> the direction that Linaro is going." (David Rusling, Linaro CTO, quoted on 
> lwn.net)
> 
> We need to address this now, otherwise it will be too late.

Absolutely agreed. OpenMAX needs to die as an interface abstraction layer.

IIRC, the last time we discussed this in Linaro, the outcome was basically
that we want to have an OpenMAX compatible library on top of V4L, so that the
Linaro members can have a checkmark in their product specs that lists them
as compatible, but we wouldn't do anything hardware specific in there, or
advocate the use of OpenMAX over v4l2 or gstreamer.

	Arnd