Many staticcheck fixes

It now passes when run as:
  staticcheck -checks all,-U1000,-ST1003,-SA5002,-SA1019 ./...

The disabled checks will be enabled later since they are less trivial to
enable, as this is already a non-trivial number of modifications.

devices/lepton/internal/internal.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
+// Package internal contains code shared between cci and lepton.
 package internal
 
 import (

devices/lepton/lepton.go

@@ -146,11 +146,13 @@ func (d *Dev) NextFrame(f *Frame) error {
 		if err := d.readFrame(f); err != nil {
 			return err
 		}
+		/*
 			if f.Metadata.FFCDesired {
 				// TODO(maruel): Automatically trigger FFC when applicable, only do if
 				// the camera has a shutter.
-			//go d.RunFFC()
+				go d.RunFFC()
 			}
+		*/
 		// Sadly the Lepton will unconditionally send 27fps, even if the effective
 		// rate is 9fps.
 		if !equalUint16(d.prevImg.Pix, f.Gray14.Pix) {

experimental/devices/as7262/as7262.go

@@ -240,12 +240,12 @@ func (d *Dev) Halt() error {
 	d.cancel()
 	// A receive can always proceed on a closed channel we can use that
 	// to signal that the running process has been canceled correctly.
-	_, _ = <-d.done
+	<-d.done
 	return nil
 }
 
 func (d *Dev) String() string {
-	return fmt.Sprintf("AMS AS7262 6 channel visible spectrum sensor")
+	return "AMS AS7262 6 channel visible spectrum sensor"
 }
 
 // Gain is the sensor gain for all bands

experimental/devices/ina219/ina219smoketest/ina219smoketest.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
+// Package ina219smoketest tests the ina219 device.
 package ina219smoketest
 
 import (

experimental/devices/inky/example_test.go

@@ -54,7 +54,7 @@ func Example() {
 		log.Fatal(err)
 	}
 
-	if err := dev.Draw(img.Bounds(), img, image.ZP); err != nil {
+	if err := dev.Draw(img.Bounds(), img, image.Point{}); err != nil {
 		log.Fatal(err)
 	}
 }

experimental/devices/inky/inky.go

@@ -57,7 +57,7 @@ func (c *Color) Set(s string) error {
 	case "white":
 		*c = White
 	default:
-		return fmt.Errorf("Unknown color %q: expected either black, red, yellow or white", s)
+		return fmt.Errorf("unknown color %q: expected either black, red, yellow or white", s)
 	}
 	return nil
 }
@@ -90,7 +90,7 @@ func (m *Model) Set(s string) error {
 	case "WHAT":
 		*m = WHAT
 	default:
-		return fmt.Errorf("Unknown model %q: expected either PHAT or WHAT", s)
+		return fmt.Errorf("unknown model %q: expected either PHAT or WHAT", s)
 	}
 	return nil
 }
@@ -278,7 +278,7 @@ func (d *Dev) Draw(dstRect image.Rectangle, src image.Image, srcPtrs image.Point
 
 // DrawAll redraws the whole display.
 func (d *Dev) DrawAll(src image.Image) error {
-	return d.Draw(d.Bounds(), src, image.ZP)
+	return d.Draw(d.Bounds(), src, image.Point{})
 }
 
 func (d *Dev) update(border byte, black []byte, red []byte) (err error) {

experimental/devices/mcp23xxx/registers.go

@@ -107,5 +107,5 @@ func (r *registerCache) getAndSetBit(bit uint8, value bool, cached bool) error {
 
 func (r *registerCache) getBit(bit uint8, cached bool) (bool, error) {
 	v, err := r.readValue(cached)
-	return 0 != (v & (1 << bit)), err
+	return (v & (1 << bit)) != 0, err
 }

experimental/devices/mcp9808/mcp9808smoketest/mcp9808smoketest.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
+// Package mcp9808smoketest implements a smoke test for the mcp9808.
 package mcp9808smoketest
 
 import (

experimental/devices/mpu9250/accelerometer/accelerometer.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
+// Package accelerometer contains constants for the MPU9250.
 package accelerometer
 
 // Valid accelerator values.

experimental/devices/mpu9250/reg/reg.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
+// Package reg defines constants for the MPU9250.
 package reg
 
 // Unsorted mix of register addresses, commands and constants.

experimental/devices/pca9685/pca9685_test.go

@@ -125,7 +125,7 @@ func TestPCA9685(t *testing.T) {
 
 func TestPCA9685_invalidCh(t *testing.T) {
 	scenario := &i2ctest.Playback{
-		Ops: append(initializationSequence()),
+		Ops: initializationSequence(),
 	}
 
 	dev, err := NewI2C(scenario, I2CAddr)

experimental/devices/unicornhd/unicornhd.go

@@ -60,7 +60,7 @@ func (device *Dev) String() string {
 // Halt sets all the pixels to black. Error is always nil.
 func (device *Dev) Halt() error {
 	black := color.RGBA{0, 0, 0, 0}
-	return device.Draw(device.Bounds(), &image.Uniform{black}, image.ZP)
+	return device.Draw(device.Bounds(), &image.Uniform{black}, image.Point{})
 }
 
 // ColorModel implements devices.Display. There's no surprise, it is

experimental/devices/unicornhd/unicornhd_test.go

@@ -164,7 +164,7 @@ func TestDrawWritesBlackImageToSpi(t *testing.T) {
 	buf := bytes.Buffer{}
 	dev, _ := New(spitest.NewRecordRaw(&buf))
 	black := color.RGBA{0, 0, 0, 0}
-	if err := dev.Draw(dev.Bounds(), &image.Uniform{black}, image.ZP); err != nil {
+	if err := dev.Draw(dev.Bounds(), &image.Uniform{black}, image.Point{}); err != nil {
 		t.Fatal(err)
 	}
 
@@ -219,7 +219,7 @@ func TestDrawWritesWhiteImageToSpi(t *testing.T) {
 	buf := bytes.Buffer{}
 	dev, _ := New(spitest.NewRecordRaw(&buf))
 	white := color.RGBA{255, 255, 255, 255}
-	if err := dev.Draw(dev.Bounds(), &image.Uniform{white}, image.ZP); err != nil {
+	if err := dev.Draw(dev.Bounds(), &image.Uniform{white}, image.Point{}); err != nil {
 		t.Fatal(err)
 	}
 
@@ -291,7 +291,7 @@ func TestDrawWritesSequenceImageToSpi(t *testing.T) {
 			img.Set(x, y, clr)
 		}
 	}
-	if err := dev.Draw(dev.Bounds(), img, image.ZP); err != nil {
+	if err := dev.Draw(dev.Bounds(), img, image.Point{}); err != nil {
 		t.Fatal(err)
 	}
 
@@ -354,7 +354,7 @@ func TestDrawSupportsPartialUpdates(t *testing.T) {
 	buf := bytes.Buffer{}
 	dev, _ := New(spitest.NewRecordRaw(&buf))
 	white := color.RGBA{0xFF, 0xFF, 0xFF, 0xFF}
-	if err := dev.Draw(image.Rect(0, 0, 3, 3), &image.Uniform{white}, image.ZP); err != nil {
+	if err := dev.Draw(image.Rect(0, 0, 3, 3), &image.Uniform{white}, image.Point{}); err != nil {
 		t.Fatal(err)
 	}