Maven+Checkstyle - Configuration file location

[Olivier Vierlinck]

We use maven+checkstyle on a multi-project.
We have defined our checks (mycheckstyle.xml) for one of the component. The 
xml file is stored right at the root of the component (next to the src and 
target folders)
in the top pom file we have:
  <plugin>
     <groupId>org.apache.maven.plugins</groupId>
     <artifactId>maven-checkstyle-plugin</artifactId>
     <configuration>
        <configLocation>mycheckstyle.xml</configLocation>
     </configuration>
  </plugin>

So we have a structure like this

  topProject
  --- pom.xml

  --- subComponent1
  --- --- src
  --- --- target
  --- --- pom.xml
  --- --- mycheckstyle.xml
  --- --- ...

  --- subComponent2
  --- --- src
  --- --- target
  --- --- pom.xml
  --- --- ...

  --- --- subsubComponent2.1
  --- --- --- src
  --- --- --- target
  --- --- --- pom.xml
  --- --- --- ...

This works fine. But now, we would like to use the same configuration file 
for ALL our component. So, we would like to have our (single) 
mycheckstyle.xml file stored only once, right under the topProject, next to 
the top pom.xml file.

How can we define that in the pom file. I tried using relative path 
(../mycheckstyle.xml), full url (file:../mycheckstyle.xml), using maven 
variables ($project.dir/mycheckstyle.xml) but without success, always with 
one or another error message from maven such as

  Unable to find location '../mycheckstyle.xml' as URL, File or Resource.

Is there any way to combine maven's knowledge of the project/components tree 
so that each individual component knwos the top level and use it to locate 
the mycheckstyle.xml. Even better: is there a way to support component with 
different level in the tree (as subComponent2 and subComponent2.1 in the 
example above)

Thanks,
Olivier