sysfs: refactor interface for better match with actual interface

Signed-off-by: deadprogram <ron@hybridgroup.com>

sysfs/pwm_pin.go

@@ -1,6 +1,7 @@
 package sysfs
 
 import (
+	"fmt"
 	"os"
 	"strconv"
 )
@@ -12,16 +13,21 @@ type PWMPinner interface {
 	// Unexport unexports the pin and releases the pin from the operating system
 	Unexport() error
 	// Enable enables/disables the PWM pin
-	Enable(val string) (err error)
+	Enable(bool) (err error)
 	// Period returns the current PWM period for pin
 	Period() (period string, err error)
-	// WriteDuty writes the duty cycle to the pin
+	// SetPeriod sets the current PWM period for pin
-	WriteDuty(duty string) (err error)
+	SetPeriod(period string) (err error)
+	// DutyCycle returns the duty cycle for the pin
+	DutyCycle() (duty float64, err error)
+	// SetDutyCycle writes the duty cycle to the pin
+	SetDutyCycle(duty float64) (err error)
 }
 
 type PWMPin struct {
 	pin     string
 	Chip    string
+	enabled bool
 	write   func(path string, data []byte) (i int, err error)
 	read    func(path string) ([]byte, error)
 }
@@ -30,6 +36,7 @@ type PWMPin struct {
 func NewPWMPin(pin int) *PWMPin {
 	return &PWMPin{
 		pin:     strconv.Itoa(pin),
+		enabled: false,
 		Chip:    "0",
 		read:    readPwmFile,
 		write:   writePwmFile}
@@ -48,8 +55,27 @@ func (p *PWMPin) Unexport() (err error) {
 }
 
 // Enable writes value to pwm enable path
-func (p *PWMPin) Enable(val string) (err error) {
+func (p *PWMPin) Enable(enable bool) (err error) {
-	_, err = p.write(p.pwmEnablePath(), []byte(val))
+	if p.enabled != enable {
+		p.enabled = enable
+		enableVal := 0
+		if enable {
+			enableVal = 1
+		}
+		_, err = p.write(p.pwmEnablePath(), []byte(fmt.Sprintf("%v", enableVal)))
+	}
+	return
+}
+
+// SetPolarityInverted writes value to pwm polarity path
+func (p *PWMPin) SetPolarityInverted(invert bool) (err error) {
+	if p.enabled {
+		polarity := "normal"
+		if invert {
+			polarity = "inverted"
+		}
+		_, err = p.write(p.pwmPolarityPath(), []byte(polarity))
+	}
 	return
 }
 
@@ -62,9 +88,25 @@ func (p *PWMPin) Period() (period string, err error) {
 	return string(buf), nil
 }
 
-// WriteDuty writes value to pwm duty cycle path
+// SetPeriod sets pwm period in nanoseconds
-func (p *PWMPin) WriteDuty(duty string) (err error) {
+func (p *PWMPin) SetPeriod(period uint32) (err error) {
-	_, err = p.write(p.pwmDutyCyclePath(), []byte(duty))
+	_, err = p.write(p.pwmPeriodPath(), []byte(fmt.Sprintf("%v", period)))
+	return
+}
+
+// DutyCycle reads from pwm duty cycle path and returns value
+func (p *PWMPin) DutyCycle() (duty string, err error) {
+	buf, err := p.read(p.pwmDutyCyclePath())
+	if err != nil {
+		return
+	}
+	return string(buf), nil
+}
+
+// SetDutyCycle writes value to pwm duty cycle path
+// duty is in nanoseconds
+func (p *PWMPin) SetDutyCycle(duty uint32) (err error) {
+	_, err = p.write(p.pwmDutyCyclePath(), []byte(fmt.Sprintf("%v", duty)))
 	return
 }
 
@@ -98,6 +140,11 @@ func (p *PWMPin) pwmEnablePath() string {
 	return p.pwmPath() + "/pwm" + p.pin + "/enable"
 }
 
+// pwmPolarityPath returns polarity path for specified pin
+func (p *PWMPin) pwmPolarityPath() string {
+	return p.pwmPath() + "/pwm" + p.pin + "/polarity"
+}
+
 func writePwmFile(path string, data []byte) (i int, err error) {
 	file, err := OpenFile(path, os.O_WRONLY, 0644)
 	defer file.Close()

sysfs/pwm_pin_test.go

@@ -15,6 +15,7 @@ func TestPwmPin(t *testing.T) {
 		"/sys/class/pwm/pwmchip0/pwm10/enable",
 		"/sys/class/pwm/pwmchip0/pwm10/period",
 		"/sys/class/pwm/pwmchip0/pwm10/duty_cycle",
+		"/sys/class/pwm/pwmchip0/pwm10/polarity",
 	})
 
 	SetFilesystem(fs)
@@ -31,7 +32,7 @@ func TestPwmPin(t *testing.T) {
 	gobottest.Assert(t, fs.Files["/sys/class/pwm/pwmchip0/export"].Contents, "10")
 
 	gobottest.Refute(t, fs.Files["/sys/class/pwm/pwmchip0/pwm10/enable"].Contents, "1")
-	err = pin.Enable("1")
+	err = pin.Enable(true)
 	gobottest.Assert(t, err, nil)
 	gobottest.Assert(t, fs.Files["/sys/class/pwm/pwmchip0/pwm10/enable"].Contents, "1")
 
@@ -39,8 +40,13 @@ func TestPwmPin(t *testing.T) {
 	data, _ := pin.Period()
 	gobottest.Assert(t, data, "6")
 
+	gobottest.Assert(t, pin.SetPolarityInverted(true), nil)
+	gobottest.Assert(t, fs.Files["/sys/class/pwm/pwmchip0/pwm10/polarity"].Contents, "inverted")
+	gobottest.Assert(t, pin.SetPolarityInverted(false), nil)
+	gobottest.Assert(t, fs.Files["/sys/class/pwm/pwmchip0/pwm10/polarity"].Contents, "normal")
+
 	gobottest.Refute(t, fs.Files["/sys/class/pwm/pwmchip0/pwm10/duty_cycle"].Contents, "1")
-	err = pin.WriteDuty("100")
+	err = pin.SetDutyCycle(100)
 	gobottest.Assert(t, err, nil)
 	gobottest.Assert(t, fs.Files["/sys/class/pwm/pwmchip0/pwm10/duty_cycle"].Contents, "100")
 }