add doc to exported functions.Exposed also the spi driver.

gpio.go

@@ -152,6 +152,7 @@ var gpioDriverInitialized bool
 var gpioDriverInstance GPIODriver
 
 // SetGpioDriver should be used only for testing purpose.It makes possible to unit test embd gpio functionality
+// it overrides the gpioDriverInstance
 func SetGpioDriver(drv GPIODriver, initialized bool) {
 	gpioDriverInstance = drv
 	gpioDriverInitialized = initialized

i2c.go

@@ -43,7 +43,8 @@ type I2CDriver interface {
 var i2cDriverInitialized bool
 var i2cDriverInstance I2CDriver
 
-// SetI2cDriver should be used only for testing purpose.It makes possible to unit test embd i2c functionality
+// SetI2cDriver should be used only for testing purpose.It makes possible to unit test embd i2c functionality.
+// it overrides the i2cDriverInstance
 func SetI2cDriver(drv I2CDriver, initialized bool) {
 	i2cDriverInstance = drv
 	i2cDriverInitialized = initialized

spi.go

@@ -56,6 +56,13 @@ type SPIDriver interface {
 var spiDriverInitialized bool
 var spiDriverInstance SPIDriver
 
+// SetSPIDriver should be used only for testing purpose.It makes possible to unit test embd spi functionality.
+// it overrides spiDriverInstance
+func SetSPIDriver(drv SPIDriver, initialized bool) {
+	spiDriverInstance = drv
+	spiDriverInitialized = initialized
+}
+
 // InitSPI initializes the SPI driver.
 func InitSPI() error {
 	if spiDriverInitialized {