[Mesa-dev] MESA_EXTENSION_OVERRIDE problem

[Ian Romanick]

On 11/19/2015 05:40 PM, Nanley Chery wrote:
> 
> On Thu, Nov 19, 2015 at 12:13 PM, Brian Paul <brianp at vmware.com
> <mailto:brianp at vmware.com>> wrote:
> 
>     Hi Nanley,
> 
>  
> Hi Brian,
>  
> 
>     Maybe you can fix an issue I have with the new extension code.
> 
>     Previously, I could do something like export
>     MESA_EXTENSION_OVERRIDE="-ARB_clear_buffer_object" and I would no
>     longer see it in the GL_EXTENSIONS string, even if it was an "always
>     on" extension.
> 
>     Now when I try that I get:
> 
>     Mesa 11.1.0-devel implementation error: Trying to disable
>     permanently enabled extensions: GL_ARB_get_texture_sub_image
>     Please report at https://bugs.freedesktop.org/enter_bug.cgi?product=Mesa
> 
>     The whole point of the "-GL_EXT_foobar" syntax was to hide an
>     extension from the application when it queries the driver's extensions.
> 
>     Can you please fix this so it works as before?
> 
> 
> I have two branches that provide the ability to disable permanently
> enabled extensions:
> 1. The first only modifies the extension strings and is located here:
> http://cgit.freedesktop.org/~nchery/mesa/commit/?h=mod_always_on
> <http://cgit.freedesktop.org/%7Enchery/mesa/commit/?h=mod_always_on>
> 2. The second modifies the extension strings and disables the extension
> within the driver (assuming appropriate the helper function is used). It
> also provides some performance benefits. :
> http://cgit.freedesktop.org/~nchery/mesa/commit/?h=init_ext_vals
> <http://cgit.freedesktop.org/%7Enchery/mesa/commit/?h=init_ext_vals>
> 
> I'd appreciate any feedback on the two approaches as I work to get the
> feature upstreamed.

I think #2 might be better, but there's a lot of churn.  I don't know
that we want that much churn right around the time of the release branch
point, and I think it would be good to have this resolved in 11.1.  I
also have a few bits of feedback in #2, so it might take a couple
iterations before that could land.

Whatever we do, I think we should create some 'make check' tests to
verify that the functionality continues to work in the future.

> Regards,
> Nanley
>  
> 
>     Thanks.
> 
>     -Brian
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