compileopts: add support for custom binary formats

Some chips (like the ESP family) have a particular image format that is
more complex than simply dumping everything in a raw image.

builder/build.go

@@ -260,19 +260,27 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(stri
 		}
 
 		// Get an Intel .hex file or .bin file from the .elf file.
-		if outext == ".hex" || outext == ".bin" || outext == ".gba" {
+		outputBinaryFormat := config.BinaryFormat(outext)
+		switch outputBinaryFormat {
+		case "elf":
+			// do nothing, file is already in ELF format
+		case "hex", "bin":
+			// Extract raw binary, either encoding it as a hex file or as a raw
+			// firmware file.
 			tmppath = filepath.Join(dir, "main"+outext)
-			err := objcopy(executable, tmppath)
+			err := objcopy(executable, tmppath, outputBinaryFormat)
 			if err != nil {
 				return err
 			}
-		} else if outext == ".uf2" {
+		case "uf2":
 			// Get UF2 from the .elf file.
 			tmppath = filepath.Join(dir, "main"+outext)
 			err := convertELFFileToUF2File(executable, tmppath, config.Target.UF2FamilyID)
 			if err != nil {
 				return err
 			}
+		default:
+			return fmt.Errorf("unknown output binary format: %s", outputBinaryFormat)
 		}
 		return action(tmppath)
 	}

builder/objcopy.go

@@ -4,7 +4,6 @@ import (
 	"debug/elf"
 	"io/ioutil"
 	"os"
-	"path/filepath"
 	"sort"
 
 	"github.com/marcinbor85/gohex"
@@ -93,7 +92,7 @@ func extractROM(path string) (uint64, []byte, error) {
 
 // objcopy converts an ELF file to a different (simpler) output file format:
 // .bin or .hex. It extracts only the .text section.
-func objcopy(infile, outfile string) error {
+func objcopy(infile, outfile, binaryFormat string) error {
 	f, err := os.OpenFile(outfile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
 	if err != nil {
 		return err
@@ -107,23 +106,20 @@ func objcopy(infile, outfile string) error {
 	}
 
 	// Write to the file, in the correct format.
-	switch filepath.Ext(outfile) {
-	case ".gba":
-		// The address is not stored in a .gba file.
-		_, err := f.Write(data)
-		return err
-	case ".bin":
-		// The address is not stored in a .bin file (therefore you
-		// should use .hex files in most cases).
-		_, err := f.Write(data)
-		return err
-	case ".hex":
+	switch binaryFormat {
+	case "hex":
+		// Intel hex file, includes the firmware start address.
 		mem := gohex.NewMemory()
 		err := mem.AddBinary(uint32(addr), data)
 		if err != nil {
 			return objcopyError{"failed to create .hex file", err}
 		}
 		return mem.DumpIntelHex(f, 16)
+	case "bin":
+		// The start address is not stored in raw firmware files (therefore you
+		// should use .hex files in most cases).
+		_, err := f.Write(data)
+		return err
 	default:
 		panic("unreachable")
 	}

compileopts/config.go

@@ -239,6 +239,31 @@ func (c *Config) Debug() bool {
 	return c.Options.Debug
 }
 
+// BinaryFormat returns an appropriate binary format, based on the file
+// extension and the configured binary format in the target JSON file.
+func (c *Config) BinaryFormat(ext string) string {
+	switch ext {
+	case ".bin", ".gba":
+		// The simplest format possible: dump everything in a raw binary file.
+		if c.Target.BinaryFormat != "" {
+			return c.Target.BinaryFormat
+		}
+		return "bin"
+	case ".hex":
+		// Similar to bin, but includes the start address and is thus usually a
+		// better format.
+		return "hex"
+	case ".uf2":
+		// Special purpose firmware format, mainly used on Adafruit boards.
+		// More information:
+		// https://github.com/Microsoft/uf2
+		return "uf2"
+	default:
+		// Use the ELF format for unrecognized file formats.
+		return "elf"
+	}
+}
+
 // Programmer returns the flash method and OpenOCD interface name given a
 // particular configuration. It may either be all configured in the target JSON
 // file or be modified using the -programmmer command-line option.

compileopts/target.go

@@ -47,6 +47,7 @@ type TargetSpec struct {
 	FlashVolume      string   `json:"msd-volume-name"`
 	FlashFilename    string   `json:"msd-firmware-name"`
 	UF2FamilyID      string   `json:"uf2-family-id"`
+	BinaryFormat     string   `json:"binary-format"`
 	OpenOCDInterface string   `json:"openocd-interface"`
 	OpenOCDTarget    string   `json:"openocd-target"`
 	OpenOCDTransport string   `json:"openocd-transport"`
@@ -128,6 +129,9 @@ func (spec *TargetSpec) copyProperties(spec2 *TargetSpec) {
 	if spec2.UF2FamilyID != "" {
 		spec.UF2FamilyID = spec2.UF2FamilyID
 	}
+	if spec2.BinaryFormat != "" {
+		spec.BinaryFormat = spec2.BinaryFormat
+	}
 	if spec2.OpenOCDInterface != "" {
 		spec.OpenOCDInterface = spec2.OpenOCDInterface
 	}