Intel Broadwell On Mesa Gets Support For A New OpenGL 4.3 Extension
Written by Michael Larabel in Mesa on 5 March 2014 at 12:12 AM EST. 2 Comments
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Intel's Mesa DRI driver on Linux has picked up support for another OpenGL 4 extension, but for now at least the hardware support is limited to the yet-to-be-released Broadwell.

The ARB_stencil_texturing extension is what's now supported by the latest Mesa 10.2-devel Git code for Mesa after previously only the API was in place without any Mesa GPU driver support. As explained via the OpenGL.org registry, the extension allows allows texturing of the stencil component of a packed depth stencil texture.

Unfortunately for Intel users right now, this extension is only hooked up for the upcoming Broadwell processors. As explained in the commit message, "On earlier hardware, we had to implement math in the shader to translate Y-tiled or untiled coordinates to W-tiled coordinates (which is what BLORP does today in order to texture from stencil buffers). On Broadwell, we can simply state that it's W-tiled in SURFACE_STATE, and adjust the pitch. This is much easier."

The good news for pre-Broadwell owners is that Topi Pohjolainen of Intel published on the Mesa mailing list in late February a set of patches implementing ARB_stencil_texturing support for Sandy Bridge and newer hardware, which will hopefully be merged soon.

At least Broadwell is looking good on Linux for when it debuts in a few months time, but officially the OpenGL compliance for the Intel Mesa driver is still at OpenGL 3.3 with a number of GL4 extensions being supported but OpenGL 4.0 support likely won't be officially reached until at least later in the year.
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Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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