minor cleanup

bbb.go

@@ -1,7 +1,6 @@
 package embd
 
 import (
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -189,7 +188,7 @@ func (p *bbbAnalogPin) Read() (int, error) {
 }
 
 func (p *bbbAnalogPin) Write(_ int) error {
-	return errors.New("gpio: not implemented")
+	return ErrFeatureNotImplemented
 }
 
 func (p *bbbAnalogPin) Close() error {

descriptor.go

@@ -29,4 +29,5 @@ func DescribeHost() (*Descriptor, error) {
 	return describer(rev), nil
 }
 
-var ErrFeatureNotSupport = errors.New("embd: feature is not supported")
+var ErrFeatureNotSupported = errors.New("embd: requested feature is not supported")
+var ErrFeatureNotImplemented = errors.New("embd: requested feature is not implemented")

gpio.go

@@ -52,7 +52,7 @@ func InitGPIO() error {
 	}
 
 	if desc.GPIODriver == nil {
-		return ErrFeatureNotSupport
+		return ErrFeatureNotSupported
 	}
 
 	gpioDriverInstance = desc.GPIODriver()

i2c.go

@@ -38,7 +38,7 @@ func InitI2C() error {
 	}
 
 	if desc.I2CDriver == nil {
-		return ErrFeatureNotSupport
+		return ErrFeatureNotSupported
 	}
 
 	i2cDriverInstance = desc.I2CDriver()

led.go

@@ -24,7 +24,7 @@ func InitLED() error {
 	}
 
 	if desc.LEDDriver == nil {
-		return ErrFeatureNotSupport
+		return ErrFeatureNotSupported
 	}
 
 	ledDriverInstance = desc.LEDDriver()