[Solved] drivers: how to find kernel built-ins?

[GNUser]

One last question about this, if you guys will indulge me.

I see a directory named  /sys/module/acpi/  which I'm assuming means that the acpi kernel module is loaded and active. But to my surprise, there is no builtin module of that name (i.e., no "acpi.ko" in modules.builtin) nor is there an external module of that name (i.e., no plain "acpi" in the output of lsmod). How can that be? I thought there was no third option: A kernel module must either be builtin or external, no?

P.S. I guess not everything listed in /sys/module/ is a kernel module? If that's the case, it's par for the course. Almost everything in life (including computing) turns out to be more complex than it seems.