linux/Documentation/devicetree/bindings/gpio/gpio-mm-lantiq.txt
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   1Lantiq SoC External Bus memory mapped GPIO controller
   2
   3By attaching hardware latches to the EBU it is possible to create output
   4only gpios. This driver configures a special memory address, which when
   5written to outputs 16 bit to the latches.
   6
   7The node describing the memory mapped GPIOs needs to be a child of the node
   8describing the "lantiq,localbus".
   9
  10Required properties:
  11- compatible : Should be "lantiq,gpio-mm-lantiq"
  12- reg : Address and length of the register set for the device
  13- #gpio-cells : Should be two.  The first cell is the pin number and
  14  the second cell is used to specify optional parameters (currently
  15  unused).
  16- gpio-controller : Marks the device node as a gpio controller.
  17
  18Optional properties:
  19- lantiq,shadow : The default value that we shall assume as already set on the
  20  shift register cascade.
  21
  22Example:
  23
  24localbus@0 {
  25        #address-cells = <2>;
  26        #size-cells = <1>;
  27        ranges = <0 0 0x0 0x3ffffff /* addrsel0 */
  28                1 0 0x4000000 0x4000010>; /* addsel1 */
  29        compatible = "lantiq,localbus", "simple-bus";
  30
  31        gpio_mm0: gpio@4000000 {
  32                compatible = "lantiq,gpio-mm";
  33                reg = <1 0x0 0x10>;
  34                gpio-controller;
  35                #gpio-cells = <2>;
  36                lantiq,shadow = <0x77f>
  37        };
  38}
  39