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| author | David S. Miller <davem@davemloft.net> | 2008-03-17 23:44:31 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2008-03-17 23:44:31 -0700 |
| commit | 2f633928cbba8a5858bb39b11e7219a41b0fbef5 (patch) | |
| tree | 9a82f4b7f2c3afe4b0208d8e44ea61bae90a7d22 /Documentation/gpio.txt | |
| parent | 5e226e4d9016daee170699f8a4188a5505021756 (diff) | |
| parent | bde4f8fa8db2abd5ac9c542d76012d0fedab050f (diff) | |
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
Diffstat (limited to 'Documentation/gpio.txt')
| -rw-r--r-- | Documentation/gpio.txt | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index 8da724e2a0f..54630095aa3 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -2,6 +2,9 @@ GPIO Interfaces This provides an overview of GPIO access conventions on Linux. +These calls use the gpio_* naming prefix. No other calls should use that +prefix, or the related __gpio_* prefix. + What is a GPIO? =============== @@ -69,11 +72,13 @@ in this document, but drivers acting as clients to the GPIO interface must not care how it's implemented.) That said, if the convention is supported on their platform, drivers should -use it when possible. Platforms should declare GENERIC_GPIO support in -Kconfig (boolean true), which multi-platform drivers can depend on when -using the include file: +use it when possible. Platforms must declare GENERIC_GPIO support in their +Kconfig (boolean true), and provide an <asm/gpio.h> file. Drivers that can't +work without standard GPIO calls should have Kconfig entries which depend +on GENERIC_GPIO. The GPIO calls are available, either as "real code" or as +optimized-away stubs, when drivers use the include file: - #include <asm/gpio.h> + #include <linux/gpio.h> If you stick to this convention then it'll be easier for other developers to see what your code is doing, and help maintain it. @@ -316,6 +321,9 @@ pulldowns integrated on some platforms. Not all platforms support them, or support them in the same way; and any given board might use external pullups (or pulldowns) so that the on-chip ones should not be used. (When a circuit needs 5 kOhm, on-chip 100 kOhm resistors won't do.) +Likewise drive strength (2 mA vs 20 mA) and voltage (1.8V vs 3.3V) is a +platform-specific issue, as are models like (not) having a one-to-one +correspondence between configurable pins and GPIOs. There are other system-specific mechanisms that are not specified here, like the aforementioned options for input de-glitching and wire-OR output. |