Reduce the number of golint comments.

Ran the following command:
    golint -min_confidence 0 ./... | grep -v ALL_CAPS | \
        grep -v underscores | grep -v 'another file'

and fixed the comments that made sense.

devices/bmxx80/bmx280smoketest/bmx280smoketest.go

@@ -173,15 +173,15 @@ func run(i2cBus i2c.Bus, i2cAddr uint16, spiPort spi.PortCloser) (err error) {
 
 	// 1°C
 	if delta.Temperature > 1000 || delta.Temperature < -1000 {
-		return fmt.Errorf("Temperature delta higher than expected (%s): I²C got %s; SPI got %s", delta.Temperature, i2cEnv.Temperature, spiEnv.Temperature)
+		return fmt.Errorf("temperature delta higher than expected (%s): I²C got %s; SPI got %s", delta.Temperature, i2cEnv.Temperature, spiEnv.Temperature)
 	}
 	// 0.1kPa
 	if delta.Pressure > 100 || delta.Pressure < -100 {
-		return fmt.Errorf("Pressure delta higher than expected (%s): I²C got %s; SPI got %s", delta.Pressure, i2cEnv.Pressure, spiEnv.Pressure)
+		return fmt.Errorf("pressure delta higher than expected (%s): I²C got %s; SPI got %s", delta.Pressure, i2cEnv.Pressure, spiEnv.Pressure)
 	}
 	// 4%rH
 	if delta.Humidity > 400 || delta.Humidity < -400 {
-		return fmt.Errorf("Humidity delta higher than expected (%s): I²C got %s; SPI got %s", delta.Humidity, i2cEnv.Humidity, spiEnv.Humidity)
+		return fmt.Errorf("humidity delta higher than expected (%s): I²C got %s; SPI got %s", delta.Humidity, i2cEnv.Humidity, spiEnv.Humidity)
 	}
 	return nil
 }

experimental/devices/ads1x15/ads1x15.go

@@ -24,6 +24,7 @@ const I2CAddr uint16 = 0x48
 // a differential reading between two pins.
 type Channel int
 
+// Value channels.
 const (
 	// Absolute reading.
 	Channel0 Channel = 4

experimental/devices/ccs811/ccs811.go

@@ -86,7 +86,7 @@ func (d *Dev) errorCodeToError(errorCode SensorErrorID) error {
 	default:
 		errorText = fmt.Sprintf("Uknwown error, code: %d", errorCode)
 	}
-	return fmt.Errorf("Sensor error: %s", errorText)
+	return fmt.Errorf("sensor error: %s", errorText)
 }
 
 // Opts holds the configuration options. The address must be 0x5A or 0x5B.
@@ -108,11 +108,11 @@ var DefaultOpts = Opts{
 // New creates a new driver for CCS811 VOC sensor.
 func New(bus i2c.Bus, opts *Opts) (*Dev, error) {
 	if opts.Addr != 0x5A && opts.Addr != 0x5B {
-		return nil, fmt.Errorf("Invalid device address, only 0x5A or 0x5B are allowed")
+		return nil, fmt.Errorf("invalid device address, only 0x5A or 0x5B are allowed")
 	}
 
 	if opts.MeasurementMode > MeasurementModeConstant250 {
-		return nil, fmt.Errorf("Invalid measurement mode")
+		return nil, fmt.Errorf("invalid measurement mode")
 	}
 
 	dev := &Dev{
@@ -122,14 +122,14 @@ func New(bus i2c.Bus, opts *Opts) (*Dev, error) {
 
 	// From boot mode to measurement mode.
 	if err := dev.StartSensorApp(); err != nil {
-		return nil, fmt.Errorf("Error transitioning from boot do app mode: %v", err)
+		return nil, fmt.Errorf("error transitioning from boot do app mode: %v", err)
 	}
 	mmp := &MeasurementModeParams{MeasurementMode: opts.MeasurementMode,
 		GenerateInterrupt: opts.InterruptWhenReady,
 		UseThreshold:      opts.UseThreshold}
 
 	if err := dev.SetMeasurementModeRegister(*mmp); err != nil {
-		return nil, fmt.Errorf("Error setting measurement mode: %v", err)
+		return nil, fmt.Errorf("error setting measurement mode: %v", err)
 	}
 
 	return dev, nil
@@ -197,10 +197,7 @@ func (d *Dev) GetMeasurementModeRegister() (MeasurementModeParams, error) {
 
 // Reset sets device into the BOOT mode.
 func (d *Dev) Reset() error {
-	if err := d.c.Tx([]byte{resetReg, 0x11, 0xE5, 0x72, 0x8A}, nil); err != nil {
+	return d.c.Tx([]byte{resetReg, 0x11, 0xE5, 0x72, 0x8A}, nil)
-		return err
-	}
-	return nil
 }
 
 // ReadStatus returns value of status register.
@@ -234,10 +231,7 @@ func (d *Dev) SetEnvironmentData(temp, humidity float32) error {
 		byte(rawTemp >> 8),
 		byte(rawTemp)}
 
-	if err := d.c.Tx(w, nil); err != nil {
+	return d.c.Tx(w, nil)
-		return err
-	}
-	return nil
 }
 
 // GetBaseline provides current baseline used by internal measurement algorithm.
@@ -288,10 +282,7 @@ func (d *Dev) GetBaseline() ([]byte, error) {
 // 2) The baseline must be written after the conditioning period
 func (d *Dev) SetBaseline(baseline []byte) error {
 	w := []byte{baselineReg, baseline[0], baseline[1]}
-	if err := d.c.Tx(w, nil); err != nil {
+	return d.c.Tx(w, nil)
-		return err
-	}
-	return nil
 }
 
 // SensorValues represents data read from the sensor.

experimental/devices/ccs811/ccs811_test.go

@@ -40,7 +40,7 @@ func TestBasicInitialisationAndDataRead(t *testing.T) {
 		if data.ECO2 != 0x102 &&
 			data.VOC != 0x203 &&
 			data.Status != 0xF &&
-			data.Error != fmt.Errorf("Sensor error: %s", "HEATER_FAULT: The Heater current in the CCS811 is not in range.") &&
+			data.Error != fmt.Errorf("sensor error: %s", "HEATER_FAULT: The Heater current in the CCS811 is not in range.") &&
 			data.RawDataCurrent != cExpected &&
 			data.RawDataVoltage != vExpected {
 			t.Fatalf("Data parsed incorrectly, got %v", data)

experimental/devices/epd/epd.go

@@ -359,11 +359,7 @@ func (d *Dev) Init() error {
 		return err
 	}
 
-	if err := d.setLut(Full); err != nil {
+	return d.setLut(Full)
-		return err
-	}
-
-	return nil
 }
 
 // Reset can be also used to awaken the device
@@ -429,11 +425,7 @@ func (d *Dev) setMemoryArea(xStart, yStart, xEnd, yEnd int) error {
 	if err := d.sendData([]byte{byte(yEnd & 0xFF)}); err != nil {
 		return err
 	}
-	if err := d.sendData([]byte{byte((yEnd >> 8) & 0xFF)}); err != nil {
+	return d.sendData([]byte{byte((yEnd >> 8) & 0xFF)})
-		return err
-	}
-
-	return nil
 }
 
 func (d *Dev) setLut(update PartialUpdate) error {

experimental/devices/hd44780/hd44780.go

@@ -71,11 +71,7 @@ func (r *Dev) Reset() error {
 		return err
 	}
 
-	if err := r.bulkSendData(initSequence, r.writeInstruction); err != nil {
+	return r.bulkSendData(initSequence, r.writeInstruction)
-		return err
-	}
-
-	return nil
 }
 
 func (r *Dev) String() string {
@@ -95,10 +91,7 @@ func (r *Dev) Halt() error {
 //	line - screen line, 0-based
 //	column - column, 0-based
 func (r *Dev) SetCursor(line uint8, column uint8) error {
-	if err := r.writeInstruction(0x80 | (line*lineTwo + column)); err != nil {
+	return r.writeInstruction(0x80 | (line*lineTwo + column))
-		return err
-	}
-	return nil
 }
 
 // Print the data string
@@ -187,20 +180,14 @@ func (r *Dev) sendInstruction() error {
 	if err := r.rsPin.Out(gpio.Low); err != nil {
 		return err
 	}
-	if err := r.enablePin.Out(gpio.Low); err != nil {
+	return r.enablePin.Out(gpio.Low)
-		return err
-	}
-	return nil
 }
 
 func (r *Dev) sendData() error {
 	if err := r.rsPin.Out(gpio.High); err != nil {
 		return err
 	}
-	if err := r.enablePin.Out(gpio.Low); err != nil {
+	return r.enablePin.Out(gpio.Low)
-		return err
-	}
-	return nil
 }
 
 func (r *Dev) writeInstruction(data uint8) error {
@@ -224,10 +211,7 @@ func (r *Dev) strobe() error {
 		return err
 	}
 	delayUs(2)
-	if err := r.enablePin.Out(gpio.Low); err != nil {
+	return r.enablePin.Out(gpio.Low)
-		return err
-	}
-	return nil
 }
 
 func delayUs(ms uint) {

experimental/devices/ht16k33/ht16k33.go

@@ -71,19 +71,14 @@ func (d *Dev) init() error {
 	}
 
 	// Set display to full brightness.
-	if err := d.SetBrightness(15); err != nil {
+	return d.SetBrightness(15)
-		return err
-	}
-	return nil
 }
 
 // SetBlink Blink display at specified frequency.
 func (d *Dev) SetBlink(freq BlinkFrequency) error {
-	if _, err := d.dev.Write([]byte{displaySetup | displayOn | byte(freq)}); err != nil {
+	_, err := d.dev.Write([]byte{displaySetup | displayOn | byte(freq)})
 	return err
 }
-	return nil
-}
 
 // SetBrightness of entire display to specified value.
 //

experimental/devices/hx711/hx711.go

@@ -30,6 +30,7 @@ var (
 // with a gain of 32.
 type InputMode int
 
+// Valid InputMode.
 const (
 	CHANNEL_A_GAIN_128 InputMode = 1
 	CHANNEL_A_GAIN_64  InputMode = 3

experimental/devices/inky/doc.go

@@ -3,7 +3,7 @@
 // that can be found in the LICENSE file.
 
 // Package inky drives an Inky pHAT E ink display.
-
+//
 // Datasheet
 //
 // Inky lacks a true datasheet, so the code here is derived from the reference

experimental/devices/inky/inky.go

@@ -28,11 +28,12 @@ const (
 // setting the border color.
 type Color int
 
+// Valid Color.
 const (
-	Black  = iota
+	Black Color = iota
-	Red    = iota
+	Red
-	Yellow = iota
+	Yellow
-	White  = iota
+	White
 )
 
 var borderColor = map[Color]byte{
@@ -45,6 +46,7 @@ var borderColor = map[Color]byte{
 // Model lists the supported e-ink display models.
 type Model int
 
+// Supported Model.
 const (
 	PHAT Model = iota
 	// TODO: Add wHAT here when supported.
@@ -61,10 +63,10 @@ type Opts struct {
 	BorderColor Color
 }
 
-// NewpHAT opens a handle to an Inky pHAT.
+// New opens a handle to an Inky pHAT.
 func New(p spi.Port, dc gpio.PinOut, reset gpio.PinOut, busy gpio.PinIn, o *Opts) (*Dev, error) {
 	if o.ModelColor != Black && o.ModelColor != Red && o.ModelColor != Yellow {
-		return nil, fmt.Errorf("Unsupported color: %v", o.ModelColor)
+		return nil, fmt.Errorf("unsupported color: %v", o.ModelColor)
 	}
 
 	c, err := p.Connect(488*physic.KiloHertz, spi.Mode0, 8)
@@ -153,11 +155,11 @@ func (d *Dev) Bounds() image.Rectangle {
 // Draw implements display.Drawer
 func (d *Dev) Draw(dstRect image.Rectangle, src image.Image, srcPtrs image.Point) error {
 	if dstRect != d.Bounds() {
-		return fmt.Errorf("Partial update not supported")
+		return fmt.Errorf("partial update not supported")
 	}
 
 	if src.Bounds() != d.Bounds() {
-		return fmt.Errorf("Image must be the same size as bounds: %v", d.Bounds())
+		return fmt.Errorf("image must be the same size as bounds: %v", d.Bounds())
 	}
 
 	b := src.Bounds()
@@ -331,7 +333,7 @@ func (d *Dev) sendCommand(command byte, data []byte) error {
 
 func (d *Dev) sendData(data []byte) error {
 	if len(data) > 4096 {
-		return fmt.Errorf("Sending more data than chunk size: %d > 4096", len(data))
+		return fmt.Errorf("sending more data than chunk size: %d > 4096", len(data))
 	}
 	if err := d.dc.Out(gpio.High); err != nil {
 		return err

experimental/devices/mcp9808/mcp9808.go

@@ -139,6 +139,7 @@ func (d *Dev) SenseContinuous(interval time.Duration) (<-chan physic.Env, error)
 	return env, nil
 }
 
+// Precision implement SenseEnv.
 func (d *Dev) Precision(e *physic.Env) {
 	switch d.res {
 	case Maximum:
@@ -339,6 +340,7 @@ func (d *Dev) setLowerAlert(t physic.Temperature) error {
 	return nil
 }
 
+// Alert represents an alert generated by the device.
 type Alert struct {
 	AlertMode  string
 	AlertLevel physic.Temperature
@@ -412,6 +414,7 @@ func alertTemperatureToBits(t physic.Temperature) (uint16, error) {
 
 type resolution uint8
 
+// Valid resolution values.
 const (
 	Maximum resolution = 0
 	Low     resolution = 1

experimental/devices/mfrc522/commands/low_level.go

@@ -96,7 +96,7 @@ func (r *LowLevel) Init() error {
 	return r.SetAntenna(true)
 }
 
-// setAntenna configures the antenna state, on/off.
+// SetAntenna configures the antenna state, on/off.
 func (r *LowLevel) SetAntenna(state bool) error {
 	if state {
 		current, err := r.DevRead(TxControlReg)

experimental/devices/mfrc522/mfrc522.go

@@ -35,6 +35,7 @@ type Key [6]byte
 // DefaultKey  provides the default bytes for card authentication for method B.
 var DefaultKey = Key{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}
 
+// TODO(maruel): Move to Opts pattern. Even golint complains about this.
 type config struct {
 	defaultTimeout time.Duration
 	beforeCall     func()

experimental/devices/mpu9250/accelerometer/accelerometer.go

@@ -1,27 +1,25 @@
 package accelerometer
 
+// Valid accelerator values.
 const (
 	ACCEL_FS_SEL_2G  = 0
 	ACCEL_FS_SEL_4G  = 8
 	ACCEL_FS_SEL_8G  = 0x10
 	ACCEL_FS_SEL_16G = 0x18
-
-	ACCEL_FS_SENS_2G  = 2.0 / 32768.0
-	ACCEL_FS_SENS_4G  = 4.0 / 32768.0
-	ACCEL_FS_SENS_8G  = 8.0 / 32768.0
-	ACCEL_FS_SENS_16G = 16.0 / 32768.0
 )
 
+// Sensitivity returns the sensitivity as float32.
 func Sensitivity(selector int) float32 {
 	switch selector {
+	default:
+		fallthrough
 	case ACCEL_FS_SEL_2G:
-		return ACCEL_FS_SENS_2G
+		return 2.0 / 32768.0
 	case ACCEL_FS_SEL_4G:
-		return ACCEL_FS_SENS_4G
+		return 4.0 / 32768.0
 	case ACCEL_FS_SEL_8G:
-		return ACCEL_FS_SENS_8G
+		return 8.0 / 32768.0
 	case ACCEL_FS_SEL_16G:
-		return ACCEL_FS_SENS_16G
+		return 16.0 / 32768.0
 	}
-	return ACCEL_FS_SENS_2G
 }

experimental/devices/mpu9250/mpu9250.go

@@ -82,15 +82,11 @@ func (m *MPU9250) Debug(f DebugF) {
 
 // Init initializes the device
 func (m *MPU9250) Init() error {
-	if err := m.transferBatch(initSequence, "error initializing %d: [%x:%x] => %v"); err != nil {
+	return m.transferBatch(initSequence, "error initializing %d: [%x:%x] => %v")
-		return err
-	}
-	return nil
 }
 
 // Calibrate Calibrates the device using maximum precision for both Gyroscope and Accelerometer.
 func (m *MPU9250) Calibrate() error {
-
 	if err := m.transferBatch(calibrateSequence, "error calibrating %d: [%x:%x] => %v"); err != nil {
 		return err
 	}

experimental/devices/mpu9250/reg/reg.go

@@ -1,5 +1,8 @@
 package reg
 
+// Unsorted mix of register addresses, commands and constants.
+//
+// TODO(maruel): Needs to be redone.
 const (
 	MPU9250_DEFAULT_ADDRESS     = 0xD1
 	MPU9250_ALT_DEFAULT_ADDRESS = 0xD2

experimental/devices/mpu9250/spi.go

@@ -49,10 +49,7 @@ func (s *SpiTransport) writeByte(address byte, value byte) error {
 	if err := s.device.Tx(buf[:], res[:]); err != nil {
 		return err
 	}
-	if err := s.cs.Out(gpio.High); err != nil {
+	return s.cs.Out(gpio.High)
-		return err
-	}
-	return nil
 }
 
 func (s *SpiTransport) writeMagReg(address byte, value byte) error {
@@ -104,7 +101,7 @@ func (s *SpiTransport) readByte(address byte) (byte, error) {
 
 func (s *SpiTransport) readUint16(address ...byte) (uint16, error) {
 	if len(address) != 2 {
-		return 0, fmt.Errorf("Only 2 bytes per read")
+		return 0, fmt.Errorf("only 2 bytes per read")
 	}
 	h, err := s.readByte(address[0])
 	if err != nil {

experimental/devices/pca9548/pca9548.go

@@ -42,7 +42,7 @@ type Dev struct {
 // New creates a new handle to a pca9548 I²C multiplexer.
 func New(bus i2c.Bus, opts *Opts) (*Dev, error) {
 	if opts.Addr < 0x70 || opts.Addr > 0x77 {
-		return nil, errors.New("Address outside valid range of 0x70-0x77")
+		return nil, errors.New("address outside valid range of 0x70-0x77")
 	}
 	d := &Dev{
 		c:          bus,

experimental/devices/rainbowhat/rainbowhat.go

@@ -176,9 +176,5 @@ func (d *Dev) Halt() error {
 		return err
 	}
 
-	if err := d.buttonC.Halt(); err != nil {
+	return d.buttonC.Halt()
-		return err
-	}
-
-	return nil
 }