only use /dev_host in pure docker/OCI environments and not in the

HA add-on.

buildroot-external/overlay/base/etc/init.d/S06InitSystem

@@ -39,15 +39,21 @@ init_system() {
         echo -n "storing user data in ${HOME_ASSISTANT_ADDON_DATA} (Home Assistant Add-On), "
         mount -o bind "${HOME_ASSISTANT_ADDON_DATA}" /usr/local
       fi
-    fi
 
-    # To avoid sharing the whole host /dev with the container we
-    # mount devtmps in /dev_host and symlink the necessary devices
-    mount -o noatime -t devtmpfs devtmpfs /dev_host
-    if [[ -d "/dev_host" ]]; then
-      for device in raw-uart raw-uart1 eq3loop mmd_bidcos mmd_hmip usb; do
-        ln -s "/dev_host/${device}" "/dev/${device}"
-      done
+      # remount /dev as rw to allow multimacd to create mmd_bidcos/mmd_hmip
+      # later on and unmount /dev_host on HA because not required.
+      mount -o rw,remount /dev
+    else
+      # docker/OCI environments
+      #
+      # To avoid sharing the whole host /dev with the container we
+      # mount devtmps in /dev_host and symlink the necessary devices
+      mount -o noatime -t devtmpfs devtmpfs /dev_host
+      if [[ -d "/dev_host" ]]; then
+        for device in raw-uart raw-uart1 eq3loop mmd_bidcos mmd_hmip usb; do
+          ln -s "/dev_host/${device}" "/dev/${device}"
+        done
+      fi
     fi
 
   fi