Merge branch 'sysfile-doc' into 'master'

document some constants in sys_file

See merge request redox-os/relibc!1379

src/header/sys_file/cbindgen.toml

@@ -1,6 +1,5 @@
-include_guard = "_SYS_FILE_H"
+include_guard = "_RELIBC_SYS_FILE_H"
 language = "C"
-style = "Tag"
 no_includes = true
 cpp_compat = true
 

src/header/sys_file/mod.rs

@@ -7,9 +7,14 @@ use crate::{
     platform::{Pal, Sys, types::c_int},
 };
 
+/// Place a shared lock.
 pub const LOCK_SH: c_int = 1;
+/// Place an exclusive lock.
 pub const LOCK_EX: c_int = 2;
+/// To make a nonblocking request, include `LOCK_NB` (by ORing) with any of
+/// `LOCK_SH`, `LOCK_EX` and `LOCK_UN`.
 pub const LOCK_NB: c_int = 4;
+/// Remove an existing lock held by this process.
 pub const LOCK_UN: c_int = 8;
 
 pub const L_SET: c_int = 0;
@@ -17,6 +22,8 @@ pub const L_INCR: c_int = 1;
 pub const L_XTND: c_int = 2;
 
 /// See <https://man7.org/linux/man-pages/man2/flock.2.html>.
+///
+/// Apply or remove an advisory lock on an open file.
 #[unsafe(no_mangle)]
 pub extern "C" fn flock(fd: c_int, operation: c_int) -> c_int {
     Sys::flock(fd, operation).map(|()| 0).or_minus_one_errno()