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Diffstat (limited to 'Documentation/gpio.txt')
| -rw-r--r-- | Documentation/gpio.txt | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index e4b6985044a..fa4dc077ae0 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -524,6 +524,13 @@ and have the following read/write attributes: is configured as an output, this value may be written; any nonzero value is treated as high. + "edge" ... reads as either "none", "rising", "falling", or + "both". Write these strings to select the signal edge(s) + that will make poll(2) on the "value" file return. + + This file exists only if the pin can be configured as an + interrupt generating input pin. + GPIO controllers have paths like /sys/class/gpio/chipchip42/ (for the controller implementing GPIOs starting at #42) and have the following read-only attributes: @@ -555,6 +562,11 @@ requested using gpio_request(): /* reverse gpio_export() */ void gpio_unexport(); + /* create a sysfs link to an exported GPIO node */ + int gpio_export_link(struct device *dev, const char *name, + unsigned gpio) + + 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 signal direction may change. This helps drivers prevent userspace code @@ -563,3 +575,8 @@ from accidentally clobbering important system state. This explicit exporting can help with debugging (by making some kinds of experiments easier), or can provide an always-there interface that's suitable for documenting as part of a board support package. + +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. |