diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index 792faa3c06cf..f783e7fed764 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -302,6 +302,8 @@ where 'flags' is currently defined to specify the following properties:
 
 	* GPIOF_INIT_LOW	- as output, set initial level to LOW
 	* GPIOF_INIT_HIGH	- as output, set initial level to HIGH
+	* GPIOF_OPEN_DRAIN	- gpio pin is open drain type.
+	* GPIOF_OPEN_SOURCE	- gpio pin is open source type.
 
 since GPIOF_INIT_* are only valid when configured as output, so group valid
 combinations as:
@@ -310,8 +312,19 @@ combinations as:
 	* GPIOF_OUT_INIT_LOW	- configured as output, initial level LOW
 	* GPIOF_OUT_INIT_HIGH	- configured as output, initial level HIGH
 
-In the future, these flags can be extended to support more properties such
-as open-drain status.
+When setting the flag as GPIOF_OPEN_DRAIN then it will assume that pins is
+open drain type. Such pins will not be driven to 1 in output mode. It is
+require to connect pull-up on such pins. By enabling this flag, gpio lib will
+make the direction to input when it is asked to set value of 1 in output mode
+to make the pin HIGH. The pin is make to LOW by driving value 0 in output mode.
+
+When setting the flag as GPIOF_OPEN_SOURCE then it will assume that pins is
+open source type. Such pins will not be driven to 0 in output mode. It is
+require to connect pull-down on such pin. By enabling this flag, gpio lib will
+make the direction to input when it is asked to set value of 0 in output mode
+to make the pin LOW. The pin is make to HIGH by driving value 1 in output mode.
+
+In the future, these flags can be extended to support more properties.
 
 Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is
 introduced to encapsulate all three fields as: