nfsd: common grace period control

[safe/jmp/linux-2.6] / Documentation / gpio.txt

diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index 8b69811..18022e2 100644 (file)
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -389,11 +389,21 @@ either NULL or the label associated with that GPIO when it was requested.
 
 Platform Support
 ----------------
-To support this framework, a platform's Kconfig will "select HAVE_GPIO_LIB"
+To support this framework, a platform's Kconfig will "select" either
+ARCH_REQUIRE_GPIOLIB or ARCH_WANT_OPTIONAL_GPIOLIB
 and arrange that its <asm/gpio.h> includes <asm-generic/gpio.h> and defines
 three functions: gpio_get_value(), gpio_set_value(), and gpio_cansleep().
 They may also want to provide a custom value for ARCH_NR_GPIOS.
 
+ARCH_REQUIRE_GPIOLIB means that the gpio-lib code will always get compiled
+into the kernel on that architecture.
+
+ARCH_WANT_OPTIONAL_GPIOLIB means the gpio-lib code defaults to off and the user
+can enable it and build it into the kernel optionally.
+
+If neither of these options are selected, the platform does not support
+GPIOs through GPIO-lib and the code cannot be enabled by the user.
+
 Trivial implementations of those functions can directly use framework
 code, which always dispatches through the gpio_chip: