access of device cgroup is optional depends on type

Signed-off-by: Ma Shimiao <[email protected]>

Author: Ma Shimiao

config-linux.md

@@ -222,11 +222,12 @@ Each entry has the following structure:
 
 * **`allow`** *(boolean, REQUIRED)* - whether the entry is allowed or denied.
 * **`type`** *(string, OPTIONAL)* - type of device: `a` (all), `c` (char), or `b` (block).
-    Unset values mean "all", mapping to `a`.
+    Unset value means "all", mapping to `a`.
 * **`major, minor`** *(int64, OPTIONAL)* - [major, minor numbers][devices] for the device.
-    Unset values mean "all", mapping to [`*` in the filesystem API][cgroup-v1-devices].
+    Unset value means "all", mapping to [`*` in the filesystem API][cgroup-v1-devices].
 * **`access`** *(string, OPTIONAL)* - cgroup permissions for device.
     A composition of `r` (read), `w` (write), and `m` (mknod).
+    * When type is not `a`, `access` is REQUIRED.
 
 #### Example