diff options
author | David Brownell <dbrownell@users.sourceforge.net> | 2010-09-10 01:38:03 +0200 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-09-10 03:57:24 +0200 |
commit | c956126c137d97acb6f4d56fa9572d0bcc84e4ed (patch) | |
tree | aad2bdd087f9b5ea2abbf633b7f61ebd326ce562 /include | |
parent | gpio: sx150x: correct and refine reset-on-probe behavior (diff) | |
download | linux-c956126c137d97acb6f4d56fa9572d0bcc84e4ed.tar.xz linux-c956126c137d97acb6f4d56fa9572d0bcc84e4ed.zip |
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 <dbrownell@users.sourceforge.net>
Cc: Eric Miao" <eric.y.miao@gmail.com>
Cc: "Ryan Mallon" <ryan@bluewatersys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/asm-generic/gpio.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h index c7376bf80b06..8ca18e26d7e3 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; } |