+/// turns a macro argument into a string constant
+#define stringify(s) __stringify(s)
+#define __stringify(s) #s
+
+
+/**
+ * Compute the number of elements of a variable length array.
+ * <code>
+ * const char *strs[] = { "a", "b", "c" };
+ * unsigned num_strs = ARRAY_SIZE(strs);
+ * </code>
+ */
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
+
+
+/**
+ * Cast a member of a structure out to the containing structure.
+ * @param ptr The pointer to the member.
+ * @param type The type of the container struct this is embedded in.
+ * @param member The name of the member within the struct.
+ *
+ * This is a mechanism which is used throughout the Linux kernel.
+ */
+#define container_of(ptr, type, member) ({ \
+ const typeof( ((type *)0)->member ) *__mptr = (ptr); \
+ (type *)( (void *) ( (char *)__mptr - offsetof(type,member) ) );})
+
+
+/**
+ * Rounds @c m up to the nearest multiple of @c n using division.
+ * @param m The value to round up to @c n.
+ * @param n Round @c m up to a multiple of this number.
+ * @returns The rounded integer value.
+ */
+#define DIV_ROUND_UP(m, n) (((m) + (n) - 1) / (n))
+
+