[Exim] SMTP AUTH against Dovecot

I'm running Exim 4.34 on Fedora Core 1, but I don't think this is
necessarily an Exim question. I'm just wondering if anyone has gotten
Exim's SMTP AUTH to work with the Dovecot IMAP server. I've tried the
standard AUTH configs that work with Courier IMAP, substituting in the
Dovecot socket name...

clear_netscape:
  driver = plaintext
  public_name = PLAIN
  server_condition = \
    ${if eq {${readsocket{/var/run/dovecot-login/default}\
    {AUTH
${strlen:login\nlogin\n$2\n$3\n}\nlogin\nlogin\n$2\n$3\n}}}{FAIL\n}
{no}{yes}}
  server_set_id = $2

But it doesn't work. And I can't find any documentation on what format
data Dovecot is expecting via that socket. Someone must have done this
already, right?

--
Rick Ennis