From c956126c137d97acb6f4d56fa9572d0bcc84e4ed Mon Sep 17 00:00:00 2001 From: David Brownell Date: Thu, 9 Sep 2010 16:38:03 -0700 Subject: gpio: doc updates There's been some recent confusion about error checking GPIO numbers. briefly, it should be handled mostly during setup, when gpio_request() is called, and NEVER by expectig gpio_is_valid to report more than never-usable GPIO numbers. [akpm@linux-foundation.org: terminate unterminated comment] Signed-off-by: David Brownell Cc: Eric Miao" Cc: "Ryan Mallon" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/gpio.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h index c7376bf80b0..8ca18e26d7e 100644 --- a/include/asm-generic/gpio.h +++ b/include/asm-generic/gpio.h @@ -16,15 +16,27 @@ * While the GPIO programming interface defines valid GPIO numbers * to be in the range 0..MAX_INT, this library restricts them to the * smaller range 0..ARCH_NR_GPIOS-1. + * + * ARCH_NR_GPIOS is somewhat arbitrary; it usually reflects the sum of + * builtin/SoC GPIOs plus a number of GPIOs on expanders; the latter is + * actually an estimate of a board-specific value. */ #ifndef ARCH_NR_GPIOS #define ARCH_NR_GPIOS 256 #endif +/* + * "valid" GPIO numbers are nonnegative and may be passed to + * setup routines like gpio_request(). only some valid numbers + * can successfully be requested and used. + * + * Invalid GPIO numbers are useful for indicating no-such-GPIO in + * platform data and other tables. + */ + static inline int gpio_is_valid(int number) { - /* only some non-negative numbers are valid */ return ((unsigned)number) < ARCH_NR_GPIOS; } -- cgit v1.2.3