How to pass in nested expression using pfgkeys

Question

I have a setup with 2 simple macros:

\documentclass[a4paper]{article}

\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{pgfkeys}

\begin{document}

\newcommand\mycmda[1]{
  \pgfkeys{/demo/mycmda, default, #1}
  \typeout{mycmda}
  hello
}

\newcommand\mycmdb[1]{
  \pgfkeys{/demo/mycmdb, default, #1}
  \typeout{mycmdb}
  world
}

\pgfkeys{
  /demo/.is family,
  /demo/mycmda/.is family,
  /demo/mycmdb/.is family
}

\pgfkeys{
  /demo/mycmda,
  foo/.estore in = \foo
}

\pgfkeys{
  /demo/mycmdb,
  bar/.estore in = \bar
}

\pgfkeys{
  /demo/mycmda,
  default/.style = {
    foo = abc
  }
}

\pgfkeys{
  /demo/mycmdb,
  default/.style = {
    bar = xyz
  }
}

% \mycmdb{bar=hello} % this works
\mycmdb{bar=\mycmda{foo=asdf}} % this errors

\end{document}

The problem is when I try to do the following:

\mycmdb{bar=\mycmda{foo=asdf}}

It gives this error:

! TeX capacity exceeded, sorry [input stack size=5000].
\pgfkeys@possiblespace #1-> \pgfkeys
                                     {/demo/mycmda, default, #1} \typeout {m...
l.52 \mycmdb{bar=\mycmda{foo=asdf}}

What I am trying to accomplish is evaluating that expression bar=\mycmda{foo=asdf} so it becomes bar=hello essentially. But instead it errors saying Use of \\mycmdb doesn't match its definition..

If I do this it works fine:

\mycmdb{bar=hello}

Wondering how to accomplish using these "nested expressions".