spi: Kconfig: Add help text

Add detailed help text for SPI support.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index b8ca2bdedd5bceadc504e0ed6594d3696d69d716..0152dff74ffc195633aec168053fe3fdb682534c 100644 (file)
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -1,5 +1,22 @@
 menuconfig SPI
        bool "SPI Support"
+       help
+         The "Serial Peripheral Interface" is a low level synchronous
+          protocol.  Chips that support SPI can have data transfer rates
+          up to several tens of Mbit/sec.  Chips are addressed with a
+          controller and a chipselect.  Most SPI slaves don't support
+          dynamic device discovery; some are even write-only or read-only.
+
+          SPI is widely used by microcontrollers to talk with sensors,
+          eeprom and flash memory, codecs and various other controller
+          chips, analog to digital (and d-to-a) converters, and more.
+          MMC and SD cards can be accessed using SPI protocol; and for
+          DataFlash cards used in MMC sockets, SPI must always be used.
+
+          SPI is one of a family of similar protocols using a four wire
+          interface (select, clock, data in, data out) including Microwire
+          (half duplex), SSP, SSI, and PSP.  This driver framework should
+          work with most such devices and controllers.
 
 if SPI