Patent enquiry - mesa floating point buffer support

[Christopher James Halse Rogers]

On Thu, 2011-10-20 at 18:12 +0100, Colin Watson wrote:
> On Fri, Jul 08, 2011 at 05:28:18PM +1000, Christopher James Halse Rogers wrote:
> > I'd like to enable mesa's floating point buffer support in the Ubuntu
> > packages (accomplished with the --enable-texture-float configure
> > option).  This allows mesa to provide additional functionality in the
> > form of the GL_ARB_texture_float¹ and ARB_color_buffer_float² GL
> > extensions.
> > 
> > These are obviously not widely used in Ubuntu currently.  As far as I'm
> > aware, the most common user would be Wine, as DirectX provides
> > equivalent functionality.
> > 
> > The patent in question is linked to from the GL extension
> > specifications, or can be found at ³.  It's not clear to me whether or
> > not enabling this code would actually infringe, as it seems that a
> > hardware rasterisation circuit is integral to the claims.  Mesa upstream
> > has been cautious with implementing this support due to this patent,
> > however.
> > 
> > [1]: http://www.opengl.org/registry/specs/ARB/texture_float.txt
> > [2]: http://www.opengl.org/registry/specs/ARB/color_buffer_float.txt
> > [3]:
> > http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=6,650,327.PN.&OS=PN/6,650,327&RS=PN/6,650,327
> 
> Hmm.
> 
> I can confirm that we have received no other communication about this
> (but we wouldn't expect to have done, since it isn't currently enabled
> in Ubuntu).
> 
> It is true that many claims of this patent are specific to hardware
> circuits.  However, claims 9 to 24 do not specify the presence of any
> particular circuitry, and my reading of them is that they would cover
> software implementations.  I am not sufficiently fluent in the language
> of OpenGL specifications to be able to tell whether those claims cover
> the two extensions in question, but they seem quite extensive.
> Unfortunately, in jurisdictions permitting software patents, I don't
> think that we can rely on the defence that these claims only cover
> hardware, unless you or a relevant expert can confirm that Mesa is only
> affected by the hardware-specific claims.

I'm not able to confirm that, and wouldn't trust my ability to be able
to determine whether or not it is the case.

> 
> The language in the "IP Status" sections of the OpenGL specifications is
> quite aggressive and explicit: "SGI will not grant the ARB royalty-free
> use of this IP for use in OpenGL, but will discuss licensing on RAND
> terms, on an individual basis with companies wishing to use this IP in
> the context of conformant OpenGL implementations. SGI does not plan to
> make any special exemption for open source implementations."
> 
> It would be interesting to know whether this patent is being actively
> enforced.

I believe it is actively enforced.  Checking out google it seems like
there has been new litigation filed since my initial email - against
HP/Dell/Lenovo[1] and Nintendo/Sony/Acer/Apple[2].

>   However, given that it's referenced from the specifications,
> and given Mesa upstream's reticence, we might have a hard time arguing
> that we were unaware of it.
> 
> What practical functionality do we lose out on by not having these GL
> extensions?

It's hard for me to accurately estimate what we miss out on for not
having this support.  Some of this is due to the backwardness of parts
of our graphics stack - to some extent people don't *expect* things to
work properly.  So, a selection of functionality that I know we miss out
on, in no particular order:

*) This functionality is required for OpenGL 3.x and above, so we'll
lose out on being able to advertise that support when Intel finish
implementing the rest of 3.0, which they hope to do soon - support could
land in the next mesa release, which we will likely ship in 12.04.

*) There are a number of WebGL demos which require floating point
support.

*) Apart from that, a large proportion of my (admittedly small) sample
of games require this support to work properly under wine - DirectX
mandates floating-point support, and real Windows applications use it.
This leads me to believe that it's plausible that *our* developers would
find uses for it, if it were available. 

[1]:
http://news.priorsmart.com/graphics-properties-holdings-v-dell-l3r7/
[2]:
http://news.priorsmart.com/graphics-properties-holdings-v-nintendo-l3qP/
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