--- /dev/null
+#ifndef LIB_ROUND_H
+#define LIB_ROUND_H
+
+/* Yields X rounded up to the nearest multiple of STEP.
+ For X >= 0, STEP >= 1 only. */
+#define ROUND_UP(X, STEP) (((X) + (STEP) - 1) / (STEP) * (STEP))
+
+/* Yields X divided by STEP, rounded up.
+ For X >= 0, STEP >= 1 only. */
+#define DIV_ROUND_UP(X, STEP) (((X) + (STEP) - 1) / (STEP))
+
+/* Yields X rounded down to the nearest multiple of STEP.
+ For X >= 0, STEP >= 1 only. */
+#define ROUND_DOWN(X, STEP) ((X) / (STEP) * (STEP))
+
+/* There is no DIV_ROUND_DOWN. It would be simply X / STEP. */
+
+#endif /* lib/round.h */