In the Linux implementation of adc-keys (drivers/input/keyboard/adc-keys.c), `press-threshold-microvolt` is not really interpreted as a threshold, but rather as the "nominal voltage" of the button. When the voltage read from the ADC is closest to a button's `press-threshold-microvolt`, the button is considered pressed.
This patch reconciles the behavior of button-adc with Linux's adc-keys such that device trees can be synchronized with minimal modifications.
Signed-off-by: Peter Cai peter@typeblog.net --- drivers/button/button-adc.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/drivers/button/button-adc.c b/drivers/button/button-adc.c index fd896c76f9d8..9c24c960e6ff 100644 --- a/drivers/button/button-adc.c +++ b/drivers/button/button-adc.c @@ -55,7 +55,7 @@ static int button_adc_of_to_plat(struct udevice *dev) struct button_uc_plat *uc_plat = dev_get_uclass_plat(dev); struct button_adc_priv *priv = dev_get_priv(dev); struct ofnode_phandle_args args; - u32 threshold, up_threshold, t; + u32 down_threshold = 0, up_threshold, voltage, t; ofnode node; int ret;
@@ -78,7 +78,7 @@ static int button_adc_of_to_plat(struct udevice *dev) return ret;
ret = ofnode_read_u32(dev_ofnode(dev), "press-threshold-microvolt", - &threshold); + &voltage); if (ret) return ret;
@@ -87,13 +87,24 @@ static int button_adc_of_to_plat(struct udevice *dev) if (ret) return ret;
- if (t > threshold) + if (t > voltage && t < up_threshold) up_threshold = t; + else if (t < voltage && t > down_threshold) + down_threshold = t; }
priv->channel = args.args[0]; - priv->min = threshold; - priv->max = up_threshold; + + /* + * Define the voltage range such that the button is only pressed + * when the voltage is closest to its own press-threshold-microvolt + */ + if (down_threshold == 0) + priv->min = 0; + else + priv->min = down_threshold + (voltage - down_threshold) / 2; + + priv->max = voltage + (up_threshold - voltage) / 2;
return ret; }