diff --git a/lib/std/c/freebsd.zig b/lib/std/c/freebsd.zig
index 3b93ccc0c0..5fcb247af3 100644
--- a/lib/std/c/freebsd.zig
+++ b/lib/std/c/freebsd.zig
@@ -2607,3 +2607,31 @@ pub const domainset = extern struct {
 
 pub extern "c" fn cpuset_getdomain(level: cpulevel_t, which: cpuwhich_t, id: id_t, len: usize, domain: *domainset_t, r: *c_int) c_int;
 pub extern "c" fn cpuset_setdomain(level: cpulevel_t, which: cpuwhich_t, id: id_t, len: usize, domain: *const domainset_t, r: c_int) c_int;
+
+const ioctl_cmd = enum(u32) {
+    VOID = 0x20000000,
+    OUT = 0x40000000,
+    IN = 0x80000000,
+    INOUT = ioctl_cmd.IN | ioctl_cmd.OUT,
+    DIRMASK = ioctl_cmd.VOID | ioctl_cmd.IN | ioctl_cmd.OUT,
+};
+
+fn ioImpl(cmd: ioctl_cmd, op: u8, nr: u8, comptime IT: type) u32 {
+    return @bitCast(u32, @enumToInt(cmd) | @intCast(u32, @truncate(u8, @sizeOf(IT))) << 16 | @intCast(u32, op) << 8 | nr);
+}
+
+pub fn IO(op: u8, nr: u8) u32 {
+    return ioImpl(ioctl_cmd.VOID, op, nr, 0);
+}
+
+pub fn IOR(op: u8, nr: u8, comptime IT: type) u32 {
+    return ioImpl(ioctl_cmd.OUT, op, nr, @sizeOf(IT));
+}
+
+pub fn IOW(op: u8, nr: u8, comptime IT: type) u32 {
+    return ioImpl(ioctl_cmd.IN, op, nr, @sizeOf(IT));
+}
+
+pub fn IOWR(op: u8, nr: u8, comptime IT: type) u32 {
+    return ioImpl(ioctl_cmd.INOUT, op, nr, @sizeOf(IT));
+}