Issue periph#60, fix onewire not present, and hanging when it is.

Author: gsexton

host_linux.go

@@ -7,5 +7,6 @@ package host
 import (
 	// Make sure required drivers are registered.
 	_ "periph.io/x/host/v3/gpioioctl"
+	_ "periph.io/x/host/v3/netlink"
 	_ "periph.io/x/host/v3/sysfs"
 )

netlink/netlink_linux.go

@@ -6,6 +6,7 @@ package netlink
 
 import (
 	"fmt"
+	"path/filepath"
 	"syscall"
 )
 
@@ -52,3 +53,17 @@ func (s *connSocket) close() error {
 	s.fd = 0
 	return syscall.Close(fd)
 }
+
+// isOneWireAvailable checks to see if the Linux onewire bus drivers are loaded.
+// It does this by looking for entries in the /sys/bus pseudo-filesystem.
+//
+// On a Raspberry Pi SBC, the onewire bus is enabled by creating entries in the
+// kernel config.txt file which is located in /boot, or /boot/firmware depending
+// on OS/kernel levels.
+func isOneWireAvailable() bool {
+	items, err := filepath.Glob("/sys/bus/w1/devices/*")
+	if err != nil || len(items) == 0 {
+		return false
+	}
+	return true
+}

netlink/netlink_other.go

@@ -28,3 +28,7 @@ func (*connSocket) recv(_ []byte) (int, error) {
 func (*connSocket) close() error {
 	return errors.New("not implemented")
 }
+
+func isOneWireAvailable() bool {
+	return false
+}

netlink/onewire.go

@@ -463,6 +463,9 @@ func (d *driver1W) After() []string {
 }
 
 func (d *driver1W) Init() (bool, error) {
+	if !isOneWireAvailable() {
+		return false, errors.New("no onewire buses found")
+	}
 	s, err := newW1Socket()
 	if err != nil {
 		return false, fmt.Errorf("netlink-onewire: failed to open socket: %v", err)