-#define KHZ(n) ((n) * 1000)
-#define MHZ(n) ((n) * 1000000)
-#define GHZ(n) ((n) * 1000000000)
+#define SR_HZ(n) (n)
+#define SR_KHZ(n) ((n) * 1000)
+#define SR_MHZ(n) ((n) * 1000000)
+#define SR_GHZ(n) ((n) * 1000000000)
+
+#define SR_HZ_TO_NS(n) (1000000000 / (n))
+
+/* libsigrok loglevels. */
+#define SR_LOG_NONE 0 /**< Output no messages at all. */
+#define SR_LOG_ERR 1 /**< Output error messages. */
+#define SR_LOG_WARN 2 /**< Output warnings. */
+#define SR_LOG_INFO 3 /**< Output informational messages. */
+#define SR_LOG_DBG 4 /**< Output debug messages. */
+#define SR_LOG_SPEW 5 /**< Output very noisy debug messages. */
+
+/*
+ * Use SR_API to mark public API symbols, and SR_PRIV for private symbols.
+ *
+ * Variables and functions marked 'static' are private already and don't
+ * need SR_PRIV. However, functions which are not static (because they need
+ * to be used in other libsigrok-internal files) but are also not meant to
+ * be part of the public libsigrok API, must use SR_PRIV.
+ *
+ * This uses the 'visibility' feature of gcc (requires gcc >= 4.0).
+ *
+ * Details: http://gcc.gnu.org/wiki/Visibility
+ */