FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/gpio/gpio-pcf857x.txt

     * PCF857x-compatible I/O expanders
     
     The PCF857x-compatible chips have "quasi-bidirectional" I/O lines that can be
     driven high by a pull-up current source or driven low to ground. This combines
     the direction and output level into a single bit per line, which can't be read
     back. We can't actually know at initialization time whether a line is configured
     (a) as output and driving the signal low/high, or (b) as input and reporting a
     low/high value, without knowing the last value written since the chip came out
     of reset (if any). The only reliable solution for setting up line direction is
    thus to do it explicitly.
    
    Required Properties:
    
      - compatible: should be one of the following.
        - "maxim,max7328": For the Maxim MAX7378
        - "maxim,max7329": For the Maxim MAX7329
        - "nxp,pca8574": For the NXP PCA8574
        - "nxp,pca8575": For the NXP PCA8575
        - "nxp,pca9670": For the NXP PCA9670
        - "nxp,pca9671": For the NXP PCA9671
        - "nxp,pca9672": For the NXP PCA9672
        - "nxp,pca9673": For the NXP PCA9673
        - "nxp,pca9674": For the NXP PCA9674
        - "nxp,pca9675": For the NXP PCA9675
        - "nxp,pcf8574": For the NXP PCF8574
        - "nxp,pcf8574a": For the NXP PCF8574A
        - "nxp,pcf8575": For the NXP PCF8575
    
      - reg: I2C slave address.
    
      - gpio-controller: Marks the device node as a gpio controller.
      - #gpio-cells: Should be 2. The first cell is the GPIO number and the second
        cell specifies GPIO flags, as defined in <dt-bindings/gpio/gpio.h>. Only the
        GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW flags are supported.
    
    Optional Properties:
    
      - lines-initial-states: Bitmask that specifies the initial state of each
      line. When a bit is set to zero, the corresponding line will be initialized to
      the input (pulled-up) state. When the  bit is set to one, the line will be
      initialized the low-level output state. If the property is not specified
      all lines will be initialized to the input state.
    
      The I/O expander can detect input state changes, and thus optionally act as
      an interrupt controller. When the expander interrupt line is connected all the
      following properties must be set. For more information please see the
      interrupt controller device tree bindings documentation available at
      Documentation/devicetree/bindings/interrupt-controller/interrupts.txt.
    
      - interrupt-controller: Identifies the node as an interrupt controller.
      - #interrupt-cells: Number of cells to encode an interrupt source, shall be 2.
      - interrupts: Interrupt specifier for the controllers interrupt.
    
    
    Please refer to gpio.txt in this directory for details of the common GPIO
    bindings used by client devices.
    
    Example: PCF8575 I/O expander node
    
            pcf8575: gpio@20 {
                    compatible = "nxp,pcf8575";
                    reg = <0x20>;
                    interrupt-parent = <&irqpin2>;
                    interrupts = <3 0>;
                    gpio-controller;
                    #gpio-cells = <2>;
                    interrupt-controller;
                    #interrupt-cells = <2>;
            };

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