Refactored Interruptable GPIO codes

Created two new Interface and hid implementation details as much as possible.

gpio.go

@@ -23,9 +23,13 @@ const (
 	High
 )
 
+// Edge trigger for GPIO Interrupt
 type Edge string
+
+// IRQ event function definition
 type IRQEvent func(pin DigitalPin)
 
+// Available Edge trigger for Interrupt
 const (
 	EdgeNone    Edge = "none"
 	EdgeRising  Edge = "rising"
@@ -33,8 +37,25 @@ const (
 	EdgeBoth    Edge = "both"
 )
 
+// InterruptPin implements access to a Interruptable capable GPIO pin.
+type InterruptPin interface {
+	// return file handler for GPIO
+	Fd() int
+
+	// Start watching this pin for interrupt
+	Watch(edge Edge, callback IRQEvent) error
+
+	// Stop watching this pin for interrupt
+	StopWatching() error
+
+	// Signal that an Interrupt has happened
+	Signal()
+}
+
 // DigitalPin implements access to a digital IO capable GPIO pin.
 type DigitalPin interface {
+	InterruptPin
+
 	// N returns the logical GPIO number.
 	N() int
 
@@ -60,11 +81,6 @@ type DigitalPin interface {
 	// PullDown pulls the pin down.
 	PullDown() error
 
-	Watch(edge Edge, callback IRQEvent) error
-	StopWatching() error
-
-	Signal()
-
 	// Close releases the resources associated with the pin.
 	Close() error
 }
@@ -116,13 +132,17 @@ type PWMPin interface {
 	Close() error
 }
 
+type GPIOInterrupt interface {
+	// Register a pin as an interrupt
+	RegisterInterrupt(p InterruptPin) error
+
+	// Unregister a pin as an interrupt
+	UnregisterInterrupt(p InterruptPin) error
+}
+
 // GPIODriver implements a generic GPIO driver.
 type GPIODriver interface {
-	// Register a pin as an interrupt pin
+	GPIOInterrupt
-	RegisterInterrupt(fd int, p DigitalPin) error
-
-	// Unregister the file handler from the Interrupt handler
-	UnregisterInterrupt(fd int) error
 
 	// Unregister unregisters the pin from the driver. Should be called when the pin is closed.
 	Unregister(string) error

gpiodriver.go

@@ -27,7 +27,7 @@ type gpioDriver struct {
 	apf analogPinFactory
 	ppf pwmPinFactory
 
-	watchEventCallbacks map[int]DigitalPin
+	watchEventCallbacks map[int]InterruptPin
 	initializedPins     map[string]pin
 }
 
@@ -40,7 +40,7 @@ func NewGPIODriver(pinMap PinMap, dpf digitalPinFactory, apf analogPinFactory, p
 		apf:    apf,
 		ppf:    ppf,
 
-		watchEventCallbacks: map[int]DigitalPin{},
+		watchEventCallbacks: map[int]InterruptPin{},
 		initializedPins:     map[string]pin{},
 	}
 	return driver
@@ -72,12 +72,14 @@ func (io *gpioDriver) initializeEpoll() {
 	}()
 }
 
-func (io *gpioDriver) RegisterInterrupt(fd int, p DigitalPin) error {
+func (io *gpioDriver) RegisterInterrupt(p InterruptPin) error {
 
 	if epollFD == 0 {
 		io.initializeEpoll()
 	}
 
+	fd := p.Fd()
+
 	var event syscall.EpollEvent
 	event.Events = syscall.EPOLLIN | (syscall.EPOLLET & 0xffffffff) | syscall.EPOLLPRI
 
@@ -96,8 +98,9 @@ func (io *gpioDriver) RegisterInterrupt(fd int, p DigitalPin) error {
 	return nil
 }
 
-func (io *gpioDriver) UnregisterInterrupt(fd int) error {
+func (io *gpioDriver) UnregisterInterrupt(p InterruptPin) error {
 
+	fd := p.Fd()
 	if err := syscall.EpollCtl(epollFD, syscall.EPOLL_CTL_DEL, fd, nil); err != nil {
 		return err
 	}

host/generic/digitalpin.go

@@ -111,6 +111,10 @@ func (p *digitalPin) activeLowFile() (*os.File, error) {
 	return p.openFile(path.Join(p.basePath(), "active_low"))
 }
 
+func (p *digitalPin) Fd() int {
+	return int(p.val.Fd())
+}
+
 func (p *digitalPin) setEdge(edge embd.Edge) error {
 	file, err := p.openFile(path.Join(p.basePath(), "edge"))
 	if err != nil {
@@ -127,11 +131,11 @@ func (p *digitalPin) Watch(edge embd.Edge, callback embd.IRQEvent) error {
 		return err
 	}
 	p.callback = callback
-	return p.drv.RegisterInterrupt(int(p.val.Fd()), p)
+	return p.drv.RegisterInterrupt(p)
 }
 
 func (p *digitalPin) StopWatching() error {
-	return p.drv.UnregisterInterrupt(int(p.val.Fd()))
+	return p.drv.UnregisterInterrupt(p)
 }
 
 func (p *digitalPin) Signal() {