i2c: Separate Kconfig option for i2c-smbus

Having a separate Kconfig option for i2c-smbus makes it possible to
build that support as a module even when i2c-core itself is built-in.
Bus drivers which implement SMBus alert should select this option, so
in most cases this option is hidden and the user doesn't have to care
about it.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Trent Piepho <tpiepho@freescale.com>

drivers/i2c/Kconfig

@@ -61,6 +61,16 @@ config I2C_HELPER_AUTO
 
 	  In doubt, say Y.
 
+config I2C_SMBUS
+	tristate "SMBus-specific protocols" if !I2C_HELPER_AUTO
+	help
+	  Say Y here if you want support for SMBus extensions to the I2C
+	  specification. At the moment, the only supported extension is
+	  the SMBus alert protocol.
+
+	  This support is also available as a module.  If so, the module
+	  will be called i2c-smbus.
+
 source drivers/i2c/algos/Kconfig
 source drivers/i2c/busses/Kconfig
 source drivers/i2c/chips/Kconfig

drivers/i2c/Makefile

@@ -3,7 +3,8 @@
 #
 
 obj-$(CONFIG_I2C_BOARDINFO)	+= i2c-boardinfo.o
-obj-$(CONFIG_I2C)		+= i2c-core.o i2c-smbus.o
+obj-$(CONFIG_I2C)		+= i2c-core.o
+obj-$(CONFIG_I2C_SMBUS)		+= i2c-smbus.o
 obj-$(CONFIG_I2C_CHARDEV)	+= i2c-dev.o
 obj-y				+= busses/ chips/ algos/