+ * Read bytes from the specified serial port.
+ *
+ * Note that this function may return after reading less than the specified
+ * number of bytes; it is the user's responsibility to iterate as necessary
+ * in this case.
+ *
+ * @param port Pointer to port structure.
+ * @param buf Buffer in which to store the bytes read.
+ * @param count Maximum number of bytes to read.
+ *
+ * @return The number of bytes read on success, or a negative error code.
+ */
+enum sp_return sp_read(struct sp_port *port, void *buf, size_t count);
+
+/**
+ * Write bytes to the specified serial port.
+ *
+ * Note that this function may return after writing less than the specified
+ * number of bytes; it is the user's responsibility to iterate as necessary
+ * in this case.
+ *
+ * @param port Pointer to port structure.
+ * @param buf Buffer containing the bytes to write.
+ * @param count Maximum number of bytes to write.
+ *
+ * @return The number of bytes written on success, or a negative error code.
+ */
+enum sp_return sp_write(struct sp_port *port, const void *buf, size_t count);
+
+/**
+ * Flush serial port buffers. Data in the selected buffer(s) is discarded.
+ *
+ * @param port Pointer to port structure.
+ * @param buffers Which buffer(s) to flush.
+ *
+ * @return SP_OK upon success, a negative error code otherwise.
+ */
+enum sp_return sp_flush(struct sp_port *port, enum sp_buffer buffers);
+
+/**
+ * Wait for buffered data to be transmitted.
+ *
+ * @param port Pointer to port structure.
+ *
+ * @return SP_OK upon success, a negative error code otherwise.
+ */
+enum sp_return sp_drain(struct sp_port *port);
+
+/**
+ * @}
+ * @defgroup Signals Port signalling operations
+ * @{
+ */
+
+/**
+ * Gets the status of the control signals for the specified port.
+ *
+ * The user should allocate a variable of type "enum sp_signal" and pass a
+ * pointer to this variable to receive the result. The result is a bitmask
+ * in which individual signals can be checked by bitwise OR with values of
+ * the sp_signal enum.
+ *
+ * @param port Pointer to port structure.
+ * @param signals Pointer to variable to receive result.
+ *
+ * @return SP_OK upon success, a negative error code otherwise.
+ */
+enum sp_return sp_get_signals(struct sp_port *port, enum sp_signal *signals);