On 28/03/15 00:43, Andrew Bresticker wrote: > Add a binding document for a generic ADC keypad. Buttons on an ADC > keypad are connected in a resistor ladder to an ADC. The binding > describes the mapping of ADC channel and voltage ranges to buttons. > > Signed-off-by: Andrew Bresticker <abrestic@xxxxxxxxxxxx> > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > Cc: Pawel Moll <pawel.moll@xxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Ian Campbell <ijc+devicetree@xxxxxxxxxxxxxx> > Cc: Kumar Gala <galak@xxxxxxxxxxxxxx> Just thinking about this, what options do we have for how such a keypad might be wired. The interesting cases are the more than one key at a time ones. If that happens, then we end up with a voltage that should allow us to work out which combination of keys is pressed. http://en.wikipedia.org/wiki/Resistor_ladder The binding as it stands only works for single keys being pressed at a time (I think!) Do we want to make it flexible enough to cope with multiple keys? I guess we'd need to model the common resistor ladder forms and provide a way of specifying the different setups in the device tree. J > --- > .../devicetree/bindings/input/adc-keys.txt | 43 ++++++++++++++++++++++ > 1 file changed, 43 insertions(+) > create mode 100644 Documentation/devicetree/bindings/input/adc-keys.txt > > diff --git a/Documentation/devicetree/bindings/input/adc-keys.txt b/Documentation/devicetree/bindings/input/adc-keys.txt > new file mode 100644 > index 0000000..c9a57de > --- /dev/null > +++ b/Documentation/devicetree/bindings/input/adc-keys.txt > @@ -0,0 +1,43 @@ > +Generic ADC keypad > +================== > + > +Required properties: > + - compatible: "adc-keys" > + - poll-interval: Polling interval time in ms. > + - io-channels: List of IIO channels used by the keypad. > + See ../iio/iio-bindings.txt for details. > + > +Optional properties: > + - autorepeat: Enable auto-repeat. > + > +Each button on the ADC keypad is represented by a sub-node. > + > +Required sub-node properties: > + - label: Descriptive name for the key. > + - linux,code: Keycode to emit. > + - channel: IIO channel (index into the 'io-channels' above) to which this > + button is attached. > + - min-voltage: Minimum voltage in uV when this key is pressed. > + - max-voltage: Maximum voltage in uV when this key is pressed. > + > +Optional sub-node properties: > + - linux,input-type: Event type this key generates. Defaults to 1 (EV_KEY) if > + not specified. > + > +Example: > + > +adc-keypad { > + compatible = "adc-keys"; > + poll-interval = <100>; > + io-channels = <&adc 0>, <&adc 1>; > + > + vol-up-button { > + label = "Volume Up"; > + linux,code = <KEY_VOLUMEUP>; > + channel = <0>; > + min-voltage = <1600000>; > + max-voltage = <1640000>; > + }; > + > + ... > +}; > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
