diff options
| author | Len Brown <len.brown@intel.com> | 2008-10-22 23:57:26 -0400 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2008-10-23 00:11:07 -0400 |
| commit | 057316cc6a5b521b332a1d7ccc871cd60c904c74 (patch) | |
| tree | 4333e608da237c73ff69b10878025cca96dcb4c8 /Documentation/gpio.txt | |
| parent | 3e2dab9a1c2deb03c311eb3f83466009147ed4d3 (diff) | |
| parent | 2515ddc6db8eb49a79f0fe5e67ff09ac7c81eab4 (diff) | |
Merge branch 'linus' into test
Conflicts:
MAINTAINERS
arch/x86/kernel/acpi/boot.c
arch/x86/kernel/acpi/sleep.c
drivers/acpi/Kconfig
drivers/pnp/Makefile
drivers/pnp/quirks.c
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/gpio.txt')
| -rw-r--r-- | Documentation/gpio.txt | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index 18022e249c5..b1b98870124 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -240,6 +240,10 @@ signal, or (b) something wrongly believes it's safe to remove drivers needed to manage a signal that's in active use. That is, requesting a GPIO can serve as a kind of lock. +Some platforms may also use knowledge about what GPIOs are active for +power management, such as by powering down unused chip sectors and, more +easily, gating off unused clocks. + These two calls are optional because not not all current Linux platforms offer such functionality in their GPIO support; a valid implementation could return success for all gpio_request() calls. Unlike the other calls, @@ -264,7 +268,7 @@ map between them using calls like: /* map GPIO numbers to IRQ numbers */ int gpio_to_irq(unsigned gpio); - /* map IRQ numbers to GPIO numbers */ + /* map IRQ numbers to GPIO numbers (avoid using this) */ int irq_to_gpio(unsigned irq); Those return either the corresponding number in the other namespace, or @@ -284,7 +288,8 @@ system wakeup capabilities. Non-error values returned from irq_to_gpio() would most commonly be used with gpio_get_value(), for example to initialize or update driver state -when the IRQ is edge-triggered. +when the IRQ is edge-triggered. Note that some platforms don't support +this reverse mapping, so you should avoid using it. Emulating Open Drain Signals |