title: Increasing AsIDBits from zero
body: <p>I would like to increase the number of AsIDBits in the Rocket-Chip from zero to eight and was wondering how that could be accomplished.</p>
  <h3>tile/BaseTile.Scala</h3>
  <pre class="lang-scala prettyprint-override"><code>trait HasNonDiplomaticTileParameters {
      implicit val p: Parameters
      //...
      def asIdBits: Int = p(ASIdBits)
      //...
  }
  </code></pre>
  <p><a href="https://github.com/chipsalliance/rocket-chip/blob/master/src/main/scala/tile/BaseTile.scala" rel="nofollow noreferrer">https://github.com/chipsalliance/rocket-chip/blob/master/src/main/scala/tile/BaseTile.scala</a></p>
  <p>I would like to implement a class like similar to those defined here</p>
  <h3>subsystem/Config.Scala</h3>
  <pre class="lang-scala prettyprint-override"><code>//...
  class WithFPUWithoutDivSqrt extends Config((site, here, up) =&gt; {
      case RocketTilesKey =&gt; up(RocketTilesKey, site) map { r =&gt;
          r.copy(core = r.core.copy(fpu = r.core.fpu.map(_.copy(divSqrt = false))))
      }
  })
  
  class WithBootROMFile(bootROMFile: String) extends Config((site, here, up) =&gt; {
      case BootROMLocated(x) =&gt; up(BootROMLocated(x), site).map(_.copy(contentFileName = bootROMFile))
  })
  
  class WithSynchronousRocketTiles extends Config((site, here, up) =&gt; {
      case RocketCrossingKey =&gt; up(RocketCrossingKey, site) map { r =&gt;
          r.copy(crossingType = SynchronousCrossing())
      }
  })
  //...
  </code></pre>
  <p><a href="https://github.com/chipsalliance/rocket-chip/blob/master/src/main/scala/subsystem/Configs.scala" rel="nofollow noreferrer">https://github.com/chipsalliance/rocket-chip/blob/master/src/main/scala/subsystem/Configs.scala</a></p>
  <p>I tried doing this</p>
  <pre class="lang-scala prettyprint-override"><code>class SetAsIDBits(n: Int) extends Config(
      (site, here, up) =&gt; {
          case ASIdBits =&gt; n
      }
  )
  </code></pre>
  <p>But got an error listed below</p>
  <pre><code>Configs.scala:272:10: not found: value ASIdBits    
  [error]     case ASIdBits =&gt; n        
  [error]          ^             
  [error] one error found   
  [error] (Compile / compileIncremental) Compilation failed  
  </code></pre>