diff options
author | David Brownell <dbrownell@users.sourceforge.net> | 2010-09-09 19:38:03 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-09-09 21:57:24 -0400 |
commit | c956126c137d97acb6f4d56fa9572d0bcc84e4ed (patch) | |
tree | aad2bdd087f9b5ea2abbf633b7f61ebd326ce562 /include/asm-generic/gpio.h | |
parent | 5affb607720d734ca572b8a77c5c7d62d3042b6f (diff) |
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/asm-generic/gpio.h')
-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 @@ | |||
16 | * While the GPIO programming interface defines valid GPIO numbers | 16 | * While the GPIO programming interface defines valid GPIO numbers |
17 | * to be in the range 0..MAX_INT, this library restricts them to the | 17 | * to be in the range 0..MAX_INT, this library restricts them to the |
18 | * smaller range 0..ARCH_NR_GPIOS-1. | 18 | * smaller range 0..ARCH_NR_GPIOS-1. |
19 | * | ||
20 | * ARCH_NR_GPIOS is somewhat arbitrary; it usually reflects the sum of | ||
21 | * builtin/SoC GPIOs plus a number of GPIOs on expanders; the latter is | ||
22 | * actually an estimate of a board-specific value. | ||
19 | */ | 23 | */ |
20 | 24 | ||
21 | #ifndef ARCH_NR_GPIOS | 25 | #ifndef ARCH_NR_GPIOS |
22 | #define ARCH_NR_GPIOS 256 | 26 | #define ARCH_NR_GPIOS 256 |
23 | #endif | 27 | #endif |
24 | 28 | ||
29 | /* | ||
30 | * "valid" GPIO numbers are nonnegative and may be passed to | ||
31 | * setup routines like gpio_request(). only some valid numbers | ||
32 | * can successfully be requested and used. | ||
33 | * | ||
34 | * Invalid GPIO numbers are useful for indicating no-such-GPIO in | ||
35 | * platform data and other tables. | ||
36 | */ | ||
37 | |||
25 | static inline int gpio_is_valid(int number) | 38 | static inline int gpio_is_valid(int number) |
26 | { | 39 | { |
27 | /* only some non-negative numbers are valid */ | ||
28 | return ((unsigned)number) < ARCH_NR_GPIOS; | 40 | return ((unsigned)number) < ARCH_NR_GPIOS; |
29 | } | 41 | } |
30 | 42 | ||