diff --git a/include/spi.h b/include/spi.h
index 3fe2e1eab2defc568079cd8a035225bbf682b18d..1638b503945071c9ccbd5486a870ac1814160779 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -37,11 +37,16 @@
 #define	SPI_LSB_FIRST	0x08			/* per-word bits-on-wire */
 #define	SPI_3WIRE	0x10			/* SI/SO signals shared */
 #define	SPI_LOOP	0x20			/* loopback mode */
+#define	SPI_SLAVE	0x40			/* slave mode */
+#define	SPI_PREAMBLE	0x80			/* Skip preamble bytes */
 
 /* SPI transfer flags */
 #define SPI_XFER_BEGIN	0x01			/* Assert CS before transfer */
 #define SPI_XFER_END	0x02			/* Deassert CS after transfer */
 
+/* Header byte that marks the start of the message */
+#define SPI_PREAMBLE_END_BYTE	0xec
+
 /*-----------------------------------------------------------------------
  * Representation of a SPI slave, i.e. what we're communicating with.
  *