gpiolib: allow user-selection

This patch adds functionality to the gpio-lib subsystem to make it
possible to enable the gpio-lib code even if the architecture code didn't
request to get it built in.

The archtitecture code does still need to implement the gpiolib accessor
functions in its asm/gpio.h file.  This patch adds the implementations for
x86 and PPC.

With these changes it is possible to run generic GPIO expansion cards on
every architecture that implements the trivial wrapper functions.  Support
for more architectures can easily be added.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: David Brownell <david-b@pacbell.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Samuel Ortiz <sameo@openedhand.com>
Cc: Kumar Gala <galak@gate.crashing.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 30 insertions, 5 deletions

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index de202dbe5300..5a355f829167 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -2,15 +2,40 @@
 # GPIO infrastructure and expanders
 #
 
-config HAVE_GPIO_LIB
+config ARCH_WANT_OPTIONAL_GPIOLIB
         bool
         help
+          Select this config option from the architecture Kconfig, if
+          it is possible to use gpiolib on the architecture, but let the
+          user decide whether to actually build it or not.
+          Select this instead of ARCH_REQUIRE_GPIOLIB, if your architecture does
+          not depend on GPIOs being available, but rather let the user
+          decide whether he needs it or not.
+
+config ARCH_REQUIRE_GPIOLIB
+        bool
+        select GPIOLIB
+        help
           Platforms select gpiolib if they use this infrastructure
           for all their GPIOs, usually starting with ones integrated
           into SOC processors.
+          Selecting this from the architecture code will cause the gpiolib
+          code to always get built in.
+
+
+
+menuconfig GPIOLIB
+        bool "GPIO Support"
+        depends on ARCH_WANT_OPTIONAL_GPIOLIB || ARCH_REQUIRE_GPIOLIB
+        select GENERIC_GPIO
+        help
+          This enables GPIO support through the generic GPIO library.
+          You only need to enable this, if you also want to enable
+          one or more of the GPIO expansion card drivers below.
+
+          If unsure, say N.
 
-menu "GPIO Support"
-        depends on HAVE_GPIO_LIB
+if GPIOLIB
 
 config DEBUG_GPIO
         bool "Debug GPIO calls"
@@ -116,4 +141,4 @@ config GPIO_MCP23S08
           SPI driver for Microchip MCP23S08 I/O expander.  This provides
           a GPIO interface supporting inputs and outputs.
 
-endmenu
+endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index eeb2f2b20282..8c45948d1fe7 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -2,7 +2,7 @@
 
 ccflags-$(CONFIG_DEBUG_GPIO)    += -DDEBUG
 
-obj-$(CONFIG_HAVE_GPIO_LIB)     += gpiolib.o
+obj-$(CONFIG_GPIOLIB)           += gpiolib.o
 
 obj-$(CONFIG_GPIO_MAX7301)      += max7301.o
 obj-$(CONFIG_GPIO_MCP23S08)     += mcp23s08.o