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authorRussell King <rmk+kernel@arm.linux.org.uk>2009-09-24 21:22:33 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2009-09-24 21:22:33 +0100
commitbaea7b946f00a291b166ccae7fcfed6c01530cc6 (patch)
tree4aa275fbdbec9c7b9b4629e8bee2bbecd3c6a6af /Documentation/gpio.txt
parentae19ffbadc1b2100285a5b5b3d0a4e0a11390904 (diff)
parent94e0fb086fc5663c38bbc0fe86d698be8314f82f (diff)
Merge branch 'origin' into for-linus
Conflicts: MAINTAINERS
Diffstat (limited to 'Documentation/gpio.txt')
-rw-r--r--Documentation/gpio.txt17
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.