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:
/* 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
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.