diff --git a/libc/include/bits/ioctl.h b/libc/include/bits/ioctl.h
index 745bbf0..9ed1292 100644
--- a/libc/include/bits/ioctl.h
+++ b/libc/include/bits/ioctl.h
@@ -26,13 +26,20 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _BITS_IOCTL_H_
-#define _BITS_IOCTL_H_
+#pragma once
+
+/**
+ * @file bits/ioctl.h
+ * @brief The ioctl() function.
+ */
 
 #include <sys/cdefs.h>
 
 __BEGIN_DECLS
 
+/**
+ * [ioctl(2)](http://man7.org/linux/man-pages/man2/ioctl.2.html) operates on device files.
+ */
 int ioctl(int __fd, int __request, ...);
 
 /*
@@ -57,5 +64,3 @@
 #endif
 
 __END_DECLS
-
-#endif