sys::eventfd enabled for FreeBSD. (#2259)

* sys::eventfd enabled for FreeBSD.

* CHANGELOG entry

Author: devnexen

changelog/2259.added.md

@@ -0,0 +1 @@
+Added `sys::eventfd` support on FreeBSD

src/sys/eventfd.rs

@@ -4,9 +4,9 @@ use std::os::unix::io::{FromRawFd, OwnedFd, AsRawFd, AsFd, RawFd, BorrowedFd};
 
 libc_bitflags! {
     pub struct EfdFlags: libc::c_int {
-        EFD_CLOEXEC; // Since Linux 2.6.27
-        EFD_NONBLOCK; // Since Linux 2.6.27
-        EFD_SEMAPHORE; // Since Linux 2.6.30
+        EFD_CLOEXEC; // Since Linux 2.6.27/FreeBSD 13.0
+        EFD_NONBLOCK; // Since Linux 2.6.27/FreeBSD 13.0
+        EFD_SEMAPHORE; // Since Linux 2.6.30/FreeBSD 13.0
     }
 }
 
@@ -81,4 +81,4 @@ impl From<EventFd> for OwnedFd {
     fn from(x: EventFd) -> OwnedFd {
         x.0
     }
-}
+}

src/sys/mod.rs

@@ -20,7 +20,7 @@ feature! {
     #[cfg(bsd)]
     pub mod event;
 
-    #[cfg(linux_android)]
+    #[cfg(any(linux_android, target_os = "freebsd"))]
     #[allow(missing_docs)]
     pub mod eventfd;
 }