> It depends on what layer you care about. At the application layer it is completely open.

I'm not down with this injection of skepticism. This is slipperly language trying to make a pretty clearly contrasted situation murky.

Sure, if you just need something to process instructions, maybe the well-defined cpu architecture is enough. But kernels need things like timers to run. They need USB hosts to attach keyboards & mice. They need GPUs to out things to screen. They need power management to not run hot. They need SD(-card) io to access storage.

Yes, you can run any code on an RPi, that is some definition of open. But it should be obvious that for this to be useful & prevalent, a lot more is required, and those layers being locked away, in proprietary systems, that we have to keep reverse-engineering usage of, is a huge detractor from civilization & it's functioning.

> you could claim that there are proprietary processes and supply chains for the hardware and material themselves

> Unless amateurs could build one from scratch you will never be satisfied.

I was not expecting slippery slope to descend quite so quickly! But perhaps you are right!

There is a lot of interest in open source chipmaking these days, and hopefully we indeed do start to see a re-opening of the foundries that lead to such growth & science in the 80's, that created so much progress. Companies like Oracle & IBM certainly seem to have similar desires, to insure that we can satisfy ourselves & learn & grow, first with OpenSPARC in 2005, and OpenPOWER in 2013 certainly indicate that some very big entities in the world see & understand the value of open, through and through. More recently, works like RISC-V & OpenROAD show architectures & processes are once again coming back into focus as a thing that people see the value in opening, in being able to work together in. Google is doing free chip fabrication runs to try to help re-grow this once proud & mighty but clearly ossifying sector that has undergone a massive wave of buy-outs & consolidation. Because we have to keep the knowledge & know-how alive & growing. Because people should be making chips. And too few are these days.

That all said, I think there's a pretty clear cut difference between what you are posting about "proprietary processes and supply chains" versus situations like what we have here, where Broadcom makes chips, then conceals & makes it difficult for anyone but a couple chosen embedded partners to understand or use those chips. It's a bit frustrating that Broadcom continues to use their own proprietary peripherals they've adapted over the decades versus using more off-the-shelf standard-operating peripherals. But it's not necessarily the proprietary bit that makes this so sticky: it's the overarchingly user-hostile attitude of this behemoth, the lengths they seemingly go through to keep amateurs out & away, in contrast to other companies that if not directly support at least don't obstruct upstreaming & open source driver development. I look at the wifi-router world, & Broadcom routers are basically get-what-you-buy now, no ability to customize or change OS. Broadcom used to allow alternate OSes, but since 802.11ac, they have more or less cut off access. This was always proprietary, but at least it was something we could learn about, interface with, but now, it is locked down.