// Host descriptor data structures. package embd import ( "errors" "fmt" "github.com/golang/glog" ) // Descriptor represents a host descriptor. type Descriptor struct { GPIODriver func() GPIODriver I2CDriver func() I2CDriver LEDDriver func() LEDDriver SPIDriver func() SPIDriver } // The Describer type is a Descriptor provider. type Describer func(rev int) *Descriptor // Describers is a global list of registered host Describers. var describers = make(map[Host]Describer) // Register makes a host describer available by the provided host key. // If Register is called twice with the same host or if describer is nil, // it panics. func Register(host Host, describer Describer) { if describer == nil { panic("embd: describer is nil") } if _, dup := describers[host]; dup { panic("embd: describer already registered") } describers[host] = describer glog.V(1).Infof("embd: host %v is registered", host) } var hostOverride Host var hostRevOverride int var hostOverriden bool // SetHost overrides the host and revision no. func SetHost(host Host, rev int) { hostOverride = host hostRevOverride = rev hostOverriden = true } // DescribeHost returns the detected host descriptor. // Can be overriden by calling SetHost though. func DescribeHost() (*Descriptor, error) { var host Host var rev int if hostOverriden { host, rev = hostOverride, hostRevOverride } else { var err 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 } // ErrFeatureNotSupported is returned when the host does not support a // particular feature. var ErrFeatureNotSupported = errors.New("embd: requested feature is not supported") // ErrFeatureNotImplemented is returned when a particular feature is supported // by the host but not implemented yet. var ErrFeatureNotImplemented = errors.New("embd: requested feature is not implemented")