cfmDamping: documentation please

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What is cfmDamping and why was it added? Does it replace

    dynamics damping="0.1" friction="0"

on all the atlas joints? Both kinds of damping seem to be applied to all body joints. Does it lead to a more accurate simulation of pure viscous damping with a fixed value? What is that viscous damping coefficient?

So everyone understands what I am talking about, here is the relevant code from gazebo/physics/ode/ODEJoint.cc
When not at joint limit:

      if (this->cfmDampingState[i] != ODEJoint::DAMPING_ACTIVE)
      {
        // add additional constraint row by fake hitting joint limit
        // then, set erp and cfm to simulate viscous joint damping
        this->SetAttribute("stop_erp", i, 0.0);
        this->SetAttribute("stop_cfm", i, 1.0 / this->dampingCoefficient);
        this->SetAttribute("hi_stop", i, 0.0);
        this->SetAttribute("lo_stop", i, 0.0);
        this->SetAttribute("hi_stop", i, 0.0);
        this->cfmDampingState[i] = ODEJoint::DAMPING_ACTIVE;
      }

The old form of damping seems still operational in gazebo/physics/Joint.cc

  double dampingForce = -this->dampingCoefficient * this->GetVelocity(0);
  this->SetForce(0, dampingForce);

We need to understand cfmDamping to get our models of your model to be correct.

Thanks, Chris