comments: var block + interface-less error

pkg/driver/availability/error.go

@@ -4,22 +4,25 @@ import (
 	"errors"
 )
 
-type Error interface {
-	Error() string
-}
-
-var ErrUnimplemented Error = errors.New("not implemented")
-var ErrBusy Error = errors.New("device or resource busy")
-var ErrNoDevice Error = errors.New("no such device")
+var (
+	ErrUnimplemented = NewError("not implemented")
+	ErrBusy          = NewError("device or resource busy")
+	ErrNoDevice      = NewError("no such device")
+)
 
 type errorString struct {
 	s string
 }
 
-func NewError(text string) Error {
+func NewError(text string) error {
 	return &errorString{text}
 }
 
+func IsError(err error) bool {
+	var target *errorString
+	return errors.As(err, &target)
+}
+
 func (e *errorString) Error() string {
 	return e.s
 }

pkg/driver/camera/camera_linux.go

@@ -353,7 +353,7 @@ func (c *camera) Properties() []prop.Media {
 	return properties
 }
 
-func (c *camera) IsAvailable() (bool, availability.Error) {
+func (c *camera) IsAvailable() (bool, error) {
 	var err error
 
 	// close the opened file descriptor as quickly as possible and in all cases, including panics

pkg/driver/driver.go

@@ -48,10 +48,10 @@ type Driver interface {
 }
 
 type AvailabilityAdapter interface {
-	IsAvailable() (bool, availability.Error)
+	IsAvailable() (bool, error)
 }
 
-func IsAvailable(d Driver) (bool, availability.Error) {
+func IsAvailable(d Driver) (bool, error) {
 	if aa, ok := d.(AvailabilityAdapter); ok {
 		return aa.IsAvailable()
 	}

pkg/driver/wrapper.go

@@ -56,7 +56,7 @@ type adapterWrapper struct {
 	id          string
 	info        Info
 	state       State
-	isAvailable func() (bool, availability.Error)
+	isAvailable func() (bool, error)
 }
 
 func (w *adapterWrapper) ID() string {
@@ -113,7 +113,7 @@ func (w *adapterWrapper) AudioRecord(p prop.Media) (r audio.Reader, err error) {
 	return
 }
 
-func (w *adapterWrapper) IsAvailable() (bool, availability.Error) {
+func (w *adapterWrapper) IsAvailable() (bool, error) {
 	if w.isAvailable == nil {
 		return false, availability.ErrUnimplemented
 	}