diff --git a/include/linux/spi/mcp23s08.h b/include/linux/spi/mcp23s08.h
index 22ef107..c42cff8 100644
--- a/include/linux/spi/mcp23s08.h
+++ b/include/linux/spi/mcp23s08.h
@@ -2,21 +2,24 @@
 /* FIXME driver should be able to handle IRQs...  */
 
 struct mcp23s08_chip_info {
-	bool	is_present;		/* true iff populated */
-	u8	pullups;		/* BIT(x) means enable pullup x */
+	bool		is_present;	/* true if populated */
+	unsigned	pullups;	/* BIT(x) means enable pullup x */
 };
 
 struct mcp23s08_platform_data {
-	/* Four slaves (numbered 0..3) can share one SPI chipselect, and
-	 * will provide 8..32 GPIOs using 1..4 gpio_chip instances.
+	/* For mcp23s08, up to 4 slaves (numbered 0..3) can share one SPI
+	 * chipselect, each providing 1 gpio_chip instance with 8 gpios.
+	 * For mpc23s17, up to 8 slaves (numbered 0..7) can share one SPI
+	 * chipselect, each providing 1 gpio_chip (port A + port B) with
+	 * 16 gpios.
 	 */
-	struct mcp23s08_chip_info	chip[4];
+	struct mcp23s08_chip_info	chip[8];
 
 	/* "base" is the number of the first GPIO.  Dynamic assignment is
 	 * not currently supported, and even if there are gaps in chip
 	 * addressing the GPIO numbers are sequential .. so for example
 	 * if only slaves 0 and 3 are present, their GPIOs range from
-	 * base to base+15.
+	 * base to base+15 (or base+31 for s17 variant).
 	 */
 	unsigned	base;