diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index 566edaa..fa4dc07 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -524,6 +524,13 @@
 		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: