succd: implement rp/dp/vent/pumpdown control

succbone/succd/gpio.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"sync"
+
+	"k8s.io/klog"
+)
+
+// gpio is an abstract GPIO output.
+type gpio interface {
+	// set returns the GPIO value. The meaning of the logic level is
+	// implementation-dependent.
+	set(state bool) error
+}
+
+// bbGPIO implements gpio using BeagleBone's built-in GPIO pins.
+//
+// The value of a GPIO is logically non-inverted: false is 0V, true is 3.3V.
+//
+// The GPIO can be repeatedly set to the same value without performance penalty
+// - only level changes are actually written to hardware registers.
+type bbGPIO struct {
+	path  string
+	mu    sync.Mutex
+	state bool
+}
+
+// newBBGPIO returns a BeagleBone GPIO for a given GPIO number.
+//
+// See the following for GPIO pin numbers ('GPIO NO.' column):
+//
+//	 https://vadl.github.io/images/bbb/P8Header.png
+//		https://vadl.github.io/images/bbb/P9Header.png
+func newBBGPIO(num int, value bool) (*bbGPIO, error) {
+	path := fmt.Sprintf("/sys/class/gpio/gpio%d", num)
+
+	if _, err := os.Stat(path); err != nil {
+		return nil, fmt.Errorf("could not access: %w", err)
+	}
+
+	pathDir := path + "/direction"
+	if err := os.WriteFile(pathDir, []byte("out"), 0); err != nil {
+		return nil, fmt.Errorf("could not set direction: %w", err)
+	}
+
+	pathValue := path + "/value"
+	res := &bbGPIO{
+		path: pathValue,
+	}
+	if err := res.set(value); err != nil {
+		return nil, fmt.Errorf("when setting initial value: %w", err)
+	}
+
+	return res, nil
+}
+
+func (b *bbGPIO) set(state bool) error {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if state && !b.state {
+		if err := os.WriteFile(b.path, []byte("1"), 0); err != nil {
+			return fmt.Errorf("could not turn on: %w", err)
+		}
+	} else if !state && b.state {
+		if err := os.WriteFile(b.path, []byte("0"), 0); err != nil {
+			return fmt.Errorf("could not turn off: %w", err)
+		}
+	}
+	b.state = state
+	return nil
+}
+
+// fakeGPIO implements a GPIO that logs state changes.
+type fakeGPIO struct {
+	desc  string
+	mu    sync.Mutex
+	state bool
+}
+
+func (b *fakeGPIO) set(state bool) error {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if state && !b.state {
+		klog.Infof("%s on", b.desc)
+	} else if !state && b.state {
+		klog.Infof("%s off", b.desc)
+	}
+	b.state = state
+	return nil
+}