> For ordinary free-and-open-source software, the source code availability largely guarantees community control. However, the same often does not apply to drivers. Even with source code availability, they're often written by vendors using NDAed information and in-house expertise about the underlying hardware design. As a result, drivers remain under a vendor's tight control.

This is not true for any upstream Linux kernel driver. They are fully open source, fully controlled by the community and not subject to any NDAs to work on. The vendor can only exert control in the form of reviews and open maintainership. This is the case for both AMD and Intel GPU drivers.

For numbers, Arch Linux bundles some ~7.5k loadable kernel drivers (which is a subset of all available, but AUR only has 8 out-of-tree drivers, out of which two are proprietary and 2-3 are community-led. "vendor-controlled" drivers are an extreme outlier on Linux.

While not true for nvidia's proprietary, closed-source driver stack, the linked open source nvidia (kernel) driver is nvidia's work-in-progress driver to be upstreamed in exactly this fashion.

> by watching what happens when you send the commands to hardware to invoke a feature unexposed by the HAL. Thus, it was found by reverse-engineering

It is true that documentation was lacking, but there was no reverse-engineering here, just standard (albeit, hacked up) driver development. "The HAL" means nothing, as it's just an random abstraction within the driver.

I used to work on proprietary network drivers for high-performance, FPGA-based NICs, and apart from it being more annoying to debug it's really no different than coding on anything else. Unless you're bringing up new IP blocks, it's mostly you and the code, not specs.

It would have been reverse-engineering if the registers and blocks weren't in the driver in the first place, but in this case all the parts were there to bring up a completely standard feature. What he did was use existing driver code to ask for what he wanted.

Not saying that it wasn't significant effort, but unless you consider "reading code you did not write" reverse-engineering (in which case all coding is reverse-engineering), then it has nothing to do with reverse-engineering, or bypassing anything. Considering this reverse-engineering is also a bit of a disservice to those that actually reverse-engineered GPUs and wrote open-source GPU drivers for them, like panfrost and recently the Apple silicon drivers.

Apart from the fact that the feature is hacked and not properly wired up (as evident by the IOMMU issue and abstraction break), the implementation flow is done exactly the same as when volunteers contribute fixes or features to other, complex open-source upstream GPU drivers, like AMDGPU. Not by reverse-engineering, nor by signing NDAs, but by reading and writing code and debugging your hardware. Stuff is just always harder in kernel mode.

> I meant "turning off (IOMMU && large BAR)". Disabling large BAR in order to use PCIe P2P is a suboptimal configuration.

The requirement is large BAR on, not off - the phrasing is a bit poor on the page, but they're trying to say that you need large bar support, and that you need IOMMU off, not that you need large bar and IOMMU off.