Samsung Exynos4 GPIO Controller Required properties: - compatible: Compatible property value should be "samsung,exynos4-gpio>". - reg: Physical base address of the controller and length of memory mapped region. - #gpio-cells: Should be 4. The syntax of the gpio specifier used by client nodes should be the following with values derived from the SoC user manual. <[phandle of the gpio controller node] [pin number within the gpio controller] [mux function] [flags and pull up/down] [drive strength]> Values for gpio specifier: - Pin number: is a value between 0 to 7. - Flags and Pull Up/Down: 0 - Pull Up/Down Disabled. 1 - Pull Down Enabled. 3 - Pull Up Enabled. Bit 16 (0x00010000) - Input is active low. - Drive Strength: 0 - 1x, 1 - 3x, 2 - 2x, 3 - 4x - gpio-controller: Specifies that the node is a gpio controller. - #address-cells: should be 1. - #size-cells: should be 1. Example: gpa0: gpio-controller@11400000 { #address-cells = <1>; #size-cells = <1>; compatible = "samsung,exynos4-gpio"; reg = <0x11400000 0x20>; #gpio-cells = <4>; gpio-controller; };