string: factorize skip_spaces and export it to be generally available

[safe/jmp/linux-2.6] / Documentation / gpio.txt

diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index e4b6985..e4e7dae 100644 (file)
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -380,7 +380,7 @@ rare; use gpiochip_remove() when it is unavoidable.
 
 Most often a gpio_chip is part of an instance-specific structure with state
 not exposed by the GPIO interfaces, such as addressing, power management,
-and more.  Chips such as codecs will have complex non-GPIO state,
+and more.  Chips such as codecs will have complex non-GPIO state.
 
 Any debugfs dump method should normally ignore signals which haven't been
 requested as GPIOs.  They can use gpiochip_is_requested(), which returns
@@ -524,7 +524,14 @@ and have the following read/write attributes:
                is configured as an output, this value may be written;
                any nonzero value is treated as high.
 
-GPIO controllers have paths like /sys/class/gpio/chipchip42/ (for the
+       "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/gpiochip42/ (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.