sys_util: Make ioctl number method a const fn

This allows us to define const variables that are the return value of
the method, which we can then use in match statements.

BUG=b:157189438
TEST=unit tests

Change-Id: I2475c59bfd43ec9ec149a6b688bf680fa2361a0b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2214962
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/sys_util/src/ioctl.rs b/sys_util/src/ioctl.rs
index f8c7604..3cf622b 100644
--- a/sys_util/src/ioctl.rs
+++ b/sys_util/src/ioctl.rs
@@ -23,13 +23,13 @@ macro_rules! ioctl_expr {
 macro_rules! ioctl_ioc_nr {
     ($name:ident, $dir:expr, $ty:expr, $nr:expr, $size:expr) => {
         #[allow(non_snake_case)]
-        pub fn $name() -> ::std::os::raw::c_ulong {
+        pub const fn $name() -> ::std::os::raw::c_ulong {
             $crate::ioctl_expr!($dir, $ty, $nr, $size)
         }
     };
     ($name:ident, $dir:expr, $ty:expr, $nr:expr, $size:expr, $($v:ident),+) => {
         #[allow(non_snake_case)]
-        pub fn $name($($v: ::std::os::raw::c_uint),+) -> ::std::os::raw::c_ulong {
+        pub const fn $name($($v: ::std::os::raw::c_uint),+) -> ::std::os::raw::c_ulong {
             $crate::ioctl_expr!($dir, $ty, $nr, $size)
         }
     };