simplify package structure

descriptor.go

@@ -0,0 +1,26 @@
+package embd
+
+import "fmt"
+
+type Descriptor struct {
+	GPIO func() GPIO
+	I2C  func() I2C
+}
+
+type Describer func(rev int) *Descriptor
+
+var Describers = map[Host]Describer{}
+
+func DescribeHost() (*Descriptor, error) {
+	host, rev, err := DetectHost()
+	if err != nil {
+		return nil, err
+	}
+
+	describer, ok := Describers[host]
+	if !ok {
+		return nil, fmt.Errorf("host: invalid host %q", host)
+	}
+
+	return describer(rev), nil
+}