spi: use a initializer if required by any host

host/bbb/bbb.go

@@ -155,6 +155,13 @@ func ensureFeatureDisabled(id string) error {
 	return fmt.Errorf("embd: could not disable feature %q", id)
 }
 
+func spiInitializer() error {
+	if err := ensureFeatureEnabled("BB-SPIDEV0"); err != nil {
+		return err
+	}
+	return nil
+}
+
 func init() {
 	embd.Register(embd.HostBBB, func(rev int) *embd.Descriptor {
 		return &embd.Descriptor{
@@ -168,7 +175,7 @@ func init() {
 				return embd.NewLEDDriver(ledMap, generic.NewLED)
 			},
 			SPIDriver: func() embd.SPIDriver {
-				return embd.NewSPIDriver(spiDeviceMinor, generic.NewSPIBus)
+				return embd.NewSPIDriver(spiDeviceMinor, generic.NewSPIBus, true, spiInitializer)
 			},
 		}
 	})

host/generic/spibus.go

@@ -53,24 +53,36 @@ type spiBus struct {
 
 	spiTransferData spiIocTransfer
 	initialized     bool
+
+	shouldInitialize bool
+	initializer      func() error
 }
 
 func spiIocMessageN(n uint32) uint32 {
 	return (spiIocMessage0 + (n * spiIocIncrementor))
 }
 
-func NewSPIBus(spiDevMinor, mode, channel byte, speed, bpw, delay int) embd.SPIBus {
+func NewSPIBus(spiDevMinor, mode, channel byte, speed, bpw, delay int, shouldInitialize bool, i func() error) embd.SPIBus {
 	return &spiBus{
-		spiDevMinor: spiDevMinor,
-		mode:        mode,
-		channel:     channel,
-		speed:       speed,
-		bpw:         bpw,
-		delayms:     delay,
+		spiDevMinor:      spiDevMinor,
+		mode:             mode,
+		channel:          channel,
+		speed:            speed,
+		bpw:              bpw,
+		delayms:          delay,
+		shouldInitialize: shouldInitialize,
+		initializer:      i,
 	}
 }
 
 func (b *spiBus) init() error {
+	if b.shouldInitialize {
+		if err := b.initializer(); err != nil {
+			return err
+		}
+		b.shouldInitialize = false
+	}
+
 	if b.initialized {
 		return nil
 	}

host/rpi/rpi.go

@@ -77,7 +77,7 @@ func init() {
 				return embd.NewLEDDriver(ledMap, generic.NewLED)
 			},
 			SPIDriver: func() embd.SPIDriver {
-				return embd.NewSPIDriver(spiDeviceMinor, generic.NewSPIBus)
+				return embd.NewSPIDriver(spiDeviceMinor, generic.NewSPIBus, false, nil)
 			},
 		}
 	})

spidriver.go

@@ -2,10 +2,12 @@ package embd
 
 import "sync"
 
-type spiBusFactory func(byte, byte, byte, int, int, int) SPIBus
+type spiBusFactory func(byte, byte, byte, int, int, int, bool, func() error) SPIBus
 
 type spiDriver struct {
-	spiDevMinor byte
+	spiDevMinor      byte
+	shouldInitialize bool
+	initializer      func() error
 
 	busMap     map[byte]SPIBus
 	busMapLock sync.Mutex
@@ -13,10 +15,12 @@ type spiDriver struct {
 	sbf spiBusFactory
 }
 
-func NewSPIDriver(spiDevMinor byte, sbf spiBusFactory) SPIDriver {
+func NewSPIDriver(spiDevMinor byte, sbf spiBusFactory, shouldInitialize bool, i func() error) SPIDriver {
 	return &spiDriver{
-		spiDevMinor: spiDevMinor,
-		sbf:         sbf,
+		spiDevMinor:      spiDevMinor,
+		sbf:              sbf,
+		shouldInitialize: shouldInitialize,
+		initializer:      i,
 	}
 }
 
@@ -24,7 +28,7 @@ func (s *spiDriver) Bus(mode, channel byte, speed, bpw, delay int) SPIBus {
 	s.busMapLock.Lock()
 	defer s.busMapLock.Unlock()
 
-	b := s.sbf(s.spiDevMinor, mode, channel, speed, bpw, delay)
+	b := s.sbf(s.spiDevMinor, mode, channel, speed, bpw, delay, s.shouldInitialize, s.initializer)
 	s.busMap[channel] = b
 	return b
 }