John Carmack's arguments against building a custom XR OS at Meta

That's what's claimed. That's what people say, yet it's just an excuse. I've heard the same sort of excuse people have, after they write a massive codebase, then say "Oops, sorry, didn't get around to documenting it".

And no, hardware is not more difficult than software to document.

If the system is complex, there's more need to document, just as with a huge codebase. On their end, they have new employees to train up, and they have to manage testing. So any excuse that silicon vendors have to deal with such immense complexity? My violin plays for them.

It’s not first party documentation that’s the problem. The problem is that they don’t share that documentation, so in order to get documentation for an “unsupported” OS a 3rd party needs to reverse engineer it.

That's obviously the wrong message. They should say "Go ask the engineering VP to get us off any other projects for another cycle while we're writing 'satisfying' documentation".

Extensive documentation comes at a price few companies are willing to pay (and that's not just a matter of resources. Look at Apple's documentation)

This way, good documentation is priced into my estimate for the project. I don't have a work item "spend a few days documenting." Nope, if I'm doing a foo then that includes documenting a foo at the same time.

Yes, you can produce a small amount of code faster if you don’t “waste” your time on documentation, but that becomes counterproductive as soon as you can no longer keep the entire codebase in your head.

    > Look at Apple's documentation

This is not impossible, but the effort and costs required are substantial and often lose out on a priority basis to just fixing or improving the product itself.

Documenting how to use or interact with it in a specific context, which often includes perspectives on interactions with other components, or e.g. protocols not explicit in the code, deciding where to draw the lines of what can assumed trivial common knowledge and what should be specified or explicitly not specified without notices not to rely on these etc. , that is a different thing.

If it wasn't, then truly as they used to say, the source code would be it's own best documentation (I am a big fan of programming for readability, but even the best readable code, while it will be correct and up to date, will never be enough nor the best for all)

This heavily depends on your niche I think. If you're writing closed source vendor software and your client's only guiding light is your documentation, it's 100% true.

If you're working on a 5 people project that evolves at a fast pace, and everyone touching the code is expected to be familiar with the domain and operations, you'll mostly leave comments (todos, meta info, external ticket links etc), not documentation per se.

The trouble with good docs is that they are work to maintain, like good code. If we decide to change this component in a substantial way soon, which we likely will, I'd have to practically rewrite the docs! Why bother?

Because the docs are part of the code. Write the docs.

I don't expect to win this crusade, but I'll keep writing docs anyway. Then later people will modify the code without modifying the docs, and so the docs will be a lie, but still useful, I think.

It's like asking three people who are not closely familiar with a component, but who have worked with it, "what is this thing, how does it work?" You will get three different answers. It would be nice if one of them were a written description straight from the horse's mouth, even if the component is now more of a camel.