rpi: use new revision parsing algo; support new 12 boards w/ RPi4

- Do not use the lookup table anymore, just use bit fields.
- Include unit test to ensure there is no regression on the previously
  supported model, leveraging the work done in previous commits.

This adds support to the following known board models:
   0x900021 // board1APlus
   0x900032 // board1BPlus
   0x9020e0 // board3APlus
   0x920092 // boardZero
   0x900061 // boardCM1
   0xa220a0 // boardCM3
   0xa52082 // board3B
   0xa22083 // board3B
   0xa02100 // boardCM3Plus
   0xa03111 // board4B
   0xb03111 // board4B
   0xc03111 // board4B

host/rpi/rpi.go

@@ -431,52 +431,74 @@ type features struct {
 }
 
 func (f *features) init(v uint32) error {
-	/*
-		r, err := parseRevision(v)
-		if err != nil {
-			return err
-		}
-	*/
-	r := v
+	r, err := parseRevision(v)
+	if err != nil {
+		return err
+	}
 	// Ignore the overclock bit.
-	r &= 0xFFFFFF
-	switch r {
-	case 0x2, 0x3: // B v1.0
+	r &^= warrantyVoid
+	switch r & boardMask {
+	case board1A:
 		f.hdrP1P26 = true
 		f.hdrAudio = true
-	case 0x4, 0x5, 0x6, // B v2.0
-		0x7, 0x8, 0x9, // A v2.0
-		0xd, 0xe, 0xf: // B v2.0
+		// Only the v2 PCB has the P5 header.
+		if r&revisionMask == 2 {
+			f.hdrP5 = true
+			f.hdrHDMI = true
+		}
+	case board1B:
 		f.hdrP1P26 = true
+		f.hdrAudio = true
 		// Only the v2 PCB has the P5 header.
-		f.hdrP5 = true
+		if r&revisionMask == 2 {
+			f.hdrP5 = true
+			f.hdrHDMI = true
+		}
+	case board1APlus:
+		f.hdrP1P40 = true
+		f.hdrAudio = true
+		f.hdrHDMI = true
+	case board1BPlus:
+		f.hdrP1P40 = true
+		f.hdrAudio = true
+		f.hdrHDMI = true
+	case board2B:
+		f.hdrP1P40 = true
 		f.hdrAudio = true
 		f.hdrHDMI = true
-	case 0x10, // B+ v1.0
-		0x12,               // A+ v1.1
-		0x13,               // B+ v1.2
-		0x15,               // A+ v1.1
-		0x90021,            // A+ v1.1
-		0x90032,            // B+ v1.2
-		0xa01040,           // 2 Model B v1.0
-		0xa01041, 0xa21041, // 2 Model B v1.1
-		0xa22042: // 2 Model B v1.2
+	case boardAlpha:
+	case boardCM1:
+		// TODO: define CM1 SODIMM header if anyone ever needs it. Please file an
+		// issue at https://github.com/google/periph/issues/new/choose
+	case board3B:
 		f.hdrP1P40 = true
 		f.hdrAudio = true
+		f.audioLeft41 = true
+		f.hdrHDMI = true
+	case boardZero:
+		f.hdrP1P40 = true
+		f.hdrHDMI = true
+	case boardCM3:
+		// Tell CM3 and CM3-Lite apart, if possible.
+		f.hdrSODIMM = true
+	case boardZeroW:
+		f.hdrP1P40 = true
 		f.hdrHDMI = true
-	case 0x900092, // Zero v1.2
-		0x900093, // Zero v1.3
-		0x920093, // Zero v1.3
-		0x9000c1: // Zero W v1.1
+	case board3BPlus:
 		f.hdrP1P40 = true
+		f.hdrAudio = true
+		f.audioLeft41 = true
+		f.hdrHDMI = true
+	case board3APlus:
+		f.hdrP1P40 = true
+		f.hdrAudio = true
+		f.audioLeft41 = true
 		f.hdrHDMI = true
-	case 0x11, // Compute Module 1
-		0x14: // Compute Module 1
-		// SODIMM not defined
-	case 0xa020a0: // Compute Module 3 v1.0
+	case boardReserved:
+	case boardCM3Plus:
+		// Tell CM3 and CM3-Lite apart, if possible.
 		f.hdrSODIMM = true
-		// tell CM3 and CM3-Lite apart, if possible
-	case 0xa02082, 0xa22082, 0xa32082, 0xa020d3: // 3 Model B v1.2, B+
+	case board4B:
 		f.hdrP1P40 = true
 		f.hdrAudio = true
 		f.audioLeft41 = true

host/rpi/rpi_test.go

@@ -117,6 +117,18 @@ func TestFeaturesInit(t *testing.T) {
 		{0xa22042, features{hdrP1P40: true, hdrAudio: true, hdrHDMI: true}},                    // board2B
 		{0xa22082, features{hdrP1P40: true, hdrAudio: true, audioLeft41: true, hdrHDMI: true}}, // board3B
 		{0xa32082, features{hdrP1P40: true, hdrAudio: true, audioLeft41: true, hdrHDMI: true}}, // board3B
+		{0x900021, features{hdrP1P40: true, hdrAudio: true, hdrHDMI: true}},                    // board1APlus
+		{0x900032, features{hdrP1P40: true, hdrAudio: true, hdrHDMI: true}},                    // board1BPlus
+		{0x9020e0, features{hdrP1P40: true, hdrAudio: true, audioLeft41: true, hdrHDMI: true}}, // board3APlus
+		{0x920092, features{hdrP1P40: true, hdrHDMI: true}},                                    // boardZero
+		{0x900061, features{}},                // boardCM1
+		{0xa220a0, features{hdrSODIMM: true}}, // boardCM3
+		{0xa52082, features{hdrP1P40: true, hdrAudio: true, audioLeft41: true, hdrHDMI: true}}, // board3B
+		{0xa22083, features{hdrP1P40: true, hdrAudio: true, audioLeft41: true, hdrHDMI: true}}, // board3B
+		{0xa02100, features{hdrSODIMM: true}},                                                  // boardCM3Plus
+		{0xa03111, features{hdrP1P40: true, hdrAudio: true, audioLeft41: true, hdrHDMI: true}}, // board4B
+		{0xb03111, features{hdrP1P40: true, hdrAudio: true, audioLeft41: true, hdrHDMI: true}}, // board4B
+		{0xc03111, features{hdrP1P40: true, hdrAudio: true, audioLeft41: true, hdrHDMI: true}}, // board4B
 	}
 	for i, line := range data {
 		f := features{}
@@ -134,18 +146,6 @@ func TestFeaturesInitErr(t *testing.T) {
 		0x0,
 		0x1,
 		0x16,
-		0x900021, // board1APlus
-		0x900032, // board1BPlus
-		0x9020e0, // board3APlus
-		0x920092, // boardZero
-		0x900061, // boardCM1
-		0xa220a0, // boardCM3
-		0xa52082, // board3B
-		0xa22083, // board3B
-		0xa02100, // boardCM3Plus
-		0xa03111, // board4B
-		0xb03111, // board4B
-		0xc03111, // board4B
 	}
 	for i, v := range data {
 		f := features{}