Commit 698dc0cf authored by Heinrich Schuchardt's avatar Heinrich Schuchardt Committed by Dmitry Torokhov
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dt-bindings: input: adc-keys: clarify description 



The current description of ADC keys is not precise enough.

"when this key is pressed" leaves it open if a key is considered pressed
below or above the threshold. This has led to confusion:
drivers/input/keyboard/adc-keys.c ignores the meaning of thresholds and
sets the key that is closest to press-threshold-microvolt.

This patch nails down the definitions and provides an interpretation of the
supplied example.

Signed-off-by: default avatarHeinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: default avatarRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201222110815.24121-1-xypron.glpk@gmx.de


Signed-off-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
parent 60159e9e

Documentation/devicetree/bindings/input/adc-keys.txt

+20 −2
Original line number Diff line number Diff line
@@ -5,7 +5,8 @@ Required properties: 
 - compatible: "adc-keys"

 - io-channels: Phandle to an ADC channel

 - io-channel-names = "buttons";

 - keyup-threshold-microvolt: Voltage at which all the keys are considered up.

 - keyup-threshold-microvolt: Voltage above or equal to which all the keys are

			      considered up.



Optional properties:

	- poll-interval: Poll interval time in milliseconds
@@ -17,7 +18,12 @@ Each button (key) is represented as a sub-node of "adc-keys": 
Required subnode-properties:

	- label: Descriptive name of the key.

	- linux,code: Keycode to emit.

	- press-threshold-microvolt: Voltage ADC input when this key is pressed.

	- press-threshold-microvolt: voltage above or equal to which this key is

				     considered pressed.



No two values of press-threshold-microvolt may be the same.

All values of press-threshold-microvolt must be less than

keyup-threshold-microvolt.



Example:
@@ -47,3 +53,15 @@ Example: 
			press-threshold-microvolt = <500000>;

		};

	};



+--------------------------------+------------------------+

| 2.000.000 <= value             | no key pressed         |

+--------------------------------+------------------------+

| 1.500.000 <= value < 2.000.000 | KEY_VOLUMEUP pressed   |

+--------------------------------+------------------------+

| 1.000.000 <= value < 1.500.000 | KEY_VOLUMEDOWN pressed |

+--------------------------------+------------------------+

|   500.000 <= value < 1.000.000 | KEY_ENTER pressed      |

+--------------------------------+------------------------+

|              value <   500.000 | no key pressed         |

+--------------------------------+------------------------+