Constant ENOTSUP 

pub const ENOTSUP: usize = 95; // 95usize

Not supported (operation not supported by this filesystem/device).

Aligned with Linux x86_64 where ENOTSUP == EOPNOTSUPP == 95, so that musl/relibc shims map 1:1. (Was wrongly 52 until 2026-08 : see docs-site/src/testing-findings.md F6.)