spi: added godoc

spi.go

@@ -1,27 +1,44 @@
+// SPI support.
+
 package embd
 
 const (
 	spiCpha = 0x01
 	spiCpol = 0x02
 
+	// SpiMode0 represents the mode0 operation (CPOL=0 CPHA=0) of spi.
 	SpiMode0 = (0 | 0)
+
+	// SpiMode0 represents the mode0 operation (CPOL=0 CPHA=1) of spi.
 	SpiMode1 = (0 | spiCpha)
+
+	// SpiMode0 represents the mode0 operation (CPOL=1 CPHA=0) of spi.
 	SpiMode2 = (spiCpol | 0)
+
+	// SpiMode0 represents the mode0 operation (CPOL=1 CPHA=1) of spi.
 	SpiMode3 = (spiCpol | spiCpha)
 )
 
+// SPI interface allows interaction with the SPI bus.
 type SPIBus interface {
+	// TransferAndRecieveData transmits data in a buffer(slice) and receives into it.
 	TransferAndRecieveData(dataBuffer []uint8) error
 
+	// ReceiveData receives data of length len into a slice.
 	ReceiveData(len int) ([]uint8, error)
 
+	// TransferAndReceiveByte transmits a byte data and receives a byte.
 	TransferAndReceiveByte(data byte) (byte, error)
 
+	// ReceiveByte receives a byte data.
 	ReceiveByte() (byte, error)
 
+	// Close releases the resources associated with the bus.
 	Close() error
 }
 
+// SPIDriver interface interacts with the host descriptors to allow us
+// control of SPI communication.
 type SPIDriver interface {
 	Bus(byte, byte, int, int, int) SPIBus
 
@@ -31,6 +48,7 @@ type SPIDriver interface {
 var spiDriverInitialized bool
 var spiDriverInstance SPIDriver
 
+// InitSPI initializes the SPI driver.
 func InitSPI() error {
 	if spiDriverInitialized {
 		return nil
@@ -51,10 +69,12 @@ func InitSPI() error {
 	return nil
 }
 
+// CloseSPI releases resources associated with the SPI driver.
 func CloseSPI() error {
 	return spiDriverInstance.Close()
 }
 
+// NewSPIBus returns a SPIBus.
 func NewSPIBus(mode, channel byte, speed, bpw, delay int) SPIBus {
 	if err := InitSPI(); err != nil {
 		panic(err)