Great question. Most hardware projects I've seen that market themselves as open source hardware provide the schematic and PCB design, but still use ICs that are proprietary. One of my companies, Tillitis, uses an FPGA as the main IC, and we provide the hardware design configured on the FPGA. Still, the FPGA itself is proprietary.
Another aspect to consider is whether you can audit and modify the design artefacts with open source tooling. If the schematics and PCB design is stored in a proprietary format I'd say that's slightly less open source hardware than if the format was KiCad EDA, which is open source. Similarly, in order to configure the HDL onto the FPGA, do you need to use 50 GB of proprietary Xilinx tooling, or can you use open tools for synthesis, place-and-route, and configuration? That also affects the level of openness in my opinion.
We can ask similar questions of open source software. People who run a Linux distribution typically don't compile packages themselves. If those packages are not reproducible from source, in what sense is the binary open source? It seems we consider it to be open source software because someone we trust claimed it was built from open source code.
You're right. It is very hard, if not impossible, to get absolute guarantees. Having said that, FPGAs can make supply chain attacks harder. See my other comments in this thread.
Great question. Most hardware projects I've seen that market themselves as open source hardware provide the schematic and PCB design, but still use ICs that are proprietary. One of my companies, Tillitis, uses an FPGA as the main IC, and we provide the hardware design configured on the FPGA. Still, the FPGA itself is proprietary.
Another aspect to consider is whether you can audit and modify the design artefacts with open source tooling. If the schematics and PCB design is stored in a proprietary format I'd say that's slightly less open source hardware than if the format was KiCad EDA, which is open source. Similarly, in order to configure the HDL onto the FPGA, do you need to use 50 GB of proprietary Xilinx tooling, or can you use open tools for synthesis, place-and-route, and configuration? That also affects the level of openness in my opinion.
We can ask similar questions of open source software. People who run a Linux distribution typically don't compile packages themselves. If those packages are not reproducible from source, in what sense is the binary open source? It seems we consider it to be open source software because someone we trust claimed it was built from open source code.