GPIO: Add support for active low

“Active low” pins have inverted state, i.e. they're “true” or 1 when
they're pulled to the ground and “false”/0 when left floating around
VCC. This is very common configuration when building interfaces with
semiconductors (like optocouplers), less so with relays where the
polarity mostly doesn't matter.

Signed-off-by: Wojciech Porczyk <wojciech.porczyk@connectpoint.pl>

Author: woju

plugin/gpio_linux.go

@@ -24,11 +24,13 @@ type gpio struct {
 // NewGpioPluginFromConfig creates a GPIO provider
 func NewGpioPluginFromConfig(ctx context.Context, other map[string]any) (Plugin, error) {
 	cc := struct {
-		Function GpioType
-		Pin      int
-		Chip     string
+		Function	GpioType
+		Pin      	int
+		ActiveLow	bool
+		Chip     	string
 	}{
-		Chip: "gpiochip0",
+		ActiveLow:	false,
+		Chip:		"gpiochip0",
 	}
 
 	if err := util.DecodeOther(other, &cc); err != nil {
@@ -38,13 +40,19 @@ func NewGpioPluginFromConfig(ctx context.Context, other map[string]any) (Plugin,
 	var opts []gpiocdev.LineReqOption
 	switch cc.Function {
 	case GpioTypeRead:
-		opts = append(opts, gpiocdev.AsInput, gpiocdev.WithPullUp)
+		opts = append(opts, gpiocdev.AsInput)
 	case GpioTypeWrite:
 		opts = append(opts, gpiocdev.AsOutput(0))
 	default:
 		return nil, fmt.Errorf("invalid type: %s", cc.Function)
 	}
 
+	if cc.ActiveLow	{
+		opts = append(opts, gpiocdev.WithPullUp, gpiocdev.AsActiveLow)
+	} else {
+		opts = append(opts, gpiocdev.WithPullDown)
+	}
+
 	line, err := gpiocdev.RequestLine(cc.Chip, cc.Pin, opts...)
 	if err != nil {
 		return nil, fmt.Errorf("failed to open GPIO: %w", err)