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| author | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2010-01-21 23:55:25 -0800 |
|---|---|---|
| committer | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2010-01-21 23:55:25 -0800 |
| commit | 7755726fe90a8b253659756e6de68c1a55aa427f (patch) | |
| tree | a3523fa77e07854db3b8089e3066a55ea997060c /Documentation/gpio.txt | |
| parent | 3bf127637e22ddf95e67e10a23c339cee3d52429 (diff) | |
| parent | 92dcffb916d309aa01778bf8963a6932e4014d07 (diff) | |
Merge commit 'v2.6.33-rc5' into next
Diffstat (limited to 'Documentation/gpio.txt')
| -rw-r--r-- | Documentation/gpio.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index e4e7daed2ba..1866c27eec6 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -531,6 +531,13 @@ and have the following read/write attributes: This file exists only if the pin can be configured as an interrupt generating input pin. + "active_low" ... reads as either 0 (false) or 1 (true). Write + any nonzero value to invert the value attribute both + for reading and writing. Existing and subsequent + poll(2) support configuration via the edge attribute + for "rising" and "falling" edges will follow this + setting. + GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the controller implementing GPIOs starting at #42) and have the following read-only attributes: @@ -566,6 +573,8 @@ requested using gpio_request(): int gpio_export_link(struct device *dev, const char *name, unsigned gpio) + /* change the polarity of a GPIO node in sysfs */ + int gpio_sysfs_set_active_low(unsigned gpio, int value); After a kernel driver requests a GPIO, it may only be made available in the sysfs interface by gpio_export(). The driver can control whether the @@ -580,3 +589,9 @@ After the GPIO has been exported, gpio_export_link() allows creating symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can use this to provide the interface under their own device in sysfs with a descriptive name. + +Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity +differences between boards from user space. This only affects the +sysfs interface. Polarity change can be done both before and after +gpio_export(), and previously enabled poll(2) support for either +rising or falling edge will be reconfigured to follow this setting. |