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Comment by zurn | Hacker News Reader

> In common with every other ARM-based SoC, using the VideoCore IV 3d graphics core on the Pi requires a block of closed-source binary driver

The Lima driver for ARM Mali is open source and runs Quake 3!

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> The Lima driver for ARM Mali is open source and runs Quake 3!

But the Lima driver was created by reverse engineering instead of using publicly available documentation.

Any open source replacement for the Raspberry Pi GPU driver is going to rely pretty heavily on reverse engineering too. The code they've released runs on the VPU, a custom-designed scalar processor within the VideoCore IV that Broadcom still haven't released architecture documentation or a toolchain for. Without a whole bunch of low-level reverse engineering (much of which was already in progress) it won't even be possible to compile the stuff Broadcom have released. Without working VPU code you can't even boot the Pi, let alone make use of graphics.

That's not correct. The code that's been released is for BCM21553, which doesn't have a VPU. There are bits and pieces of VPU assembler in there, but they're unused on the ARM target. The intention is that people port this (ARM-based) drop to run on the ARM on BCM2835. No reverse engineering required.

Ah, that makes more sense, thanks! There's an awful lot of vestigial VPU-related stuff lying around the source tree, including what I'm guessing are the unused remnants of a dead build system...

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