X-Git-Url: http://pileus.org/git/?a=blobdiff_plain;f=Documentation%2Fgpio.txt;h=1866c27eec693e7e88f7420e3ac895079cba02d9;hb=9c6a6b3cbcbbe39a018aba7f1b2b76e67cba0e9f;hp=e4e7daed2ba88dc2dbf7d0bf9c9eb16037e3e6c7;hpb=de8853bc38ceab1fa7e7f723b21430d4aad60fea;p=~andy%2Flinux

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.