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

I've written a lot of low level software, BSPs, and most of an OS, and the main reason to not write your own OS these days is silicon vendors. Back in the day, they would provide you a spec detailed enough that you could feasibly write your own drivers.

These days, you get a medium-level description and a Linux driver of questionable quality. Part of this is just laziness, but mostly this is a function of complexity. Modern hardware is just so complicated it would take a long time to completely document, and even longer to write a driver for.

At least for certain types of OSes, it should be relatively easy to get most of Linux's hardware support by porting LKL (https://github.com/lkl/linux) and adding appropriate hooks to access hardware.

Of course, your custom kernel will still have to have some of its own code to support core platform/chipset devices, but LKL should pretty much cover just about all I/O devices (and you also get stuff like disk filesystems and a network stack along with the device drivers).

Also, it probably wouldn't work so well for typical monolithic kernels, but it should work decently on something that has user-mode driver support.

>but LKL should pretty much cover just about all I/O devices (and you also get stuff like disk filesystems and a network stack along with the device drivers).

thus calling into question why you ever bothered writing a new kernel in the first place if you were just going to piggyback Linux's device drivers onto some userspace wrapper thingy.

Im not necessarily indoctrinated to the point where I can't conceive of Linux being suboptimal in a way which is so fundamental that it requires no less than a completely new OS from scratch but you're never going to get there off of recycling linux's device drivers because that forces you to design your new OS as a linux clone in which cade you definitely did not need to write an entire new kernel from scratch.