First implementation

vendor/periph.io/x/periph/periph_serial.go

@@ -0,0 +1,55 @@
+// Copyright 2018 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+// This file contains the single threaded driver loading code, to be used on
+// low performance cores.
+
+// +build tinygo
+
+package periph
+
+import (
+	"errors"
+	"strconv"
+)
+
+func initImpl() (*State, error) {
+	state = &State{}
+	// At this point, byName is guaranteed to be immutable.
+	stages, err := explodeStages()
+	if err != nil {
+		return state, err
+	}
+	loaded := make(map[string]struct{}, len(byName))
+	for _, s := range stages {
+		s.loadSerial(state, loaded)
+	}
+	return state, nil
+}
+
+// loadSerial loads all the drivers for this stage, one after the other.
+func (s *stage) loadSerial(state *State, loaded map[string]struct{}) {
+	for name, drv := range s.drvs {
+		// Intentionally do not look at After(), only Prerequisites().
+		for _, dep := range drv.Prerequisites() {
+			if _, ok := loaded[dep]; !ok {
+				state.Skipped = insertDriverFailure(state.Skipped, DriverFailure{drv, errors.New("dependency not loaded: " + strconv.Quote(dep))})
+				goto loop
+			}
+		}
+
+		// Not skipped driver, attempt loading in a goroutine.
+		if ok, err := drv.Init(); ok {
+			if err == nil {
+				state.Loaded = insertDriver(state.Loaded, drv)
+				loaded[name] = struct{}{}
+			} else {
+				state.Failed = insertDriverFailure(state.Failed, DriverFailure{drv, err})
+			}
+		} else {
+			state.Skipped = insertDriverFailure(state.Skipped, DriverFailure{drv, err})
+		}
+	loop:
+	}
+}