Not quite ideal, but this seems to be the most straightforward way to
know when someone is trying to monitor the preec stream on a channel.
This callback allows the board driver providing the span an opportunity
to setup the hardware preecho monitoring as needed.
Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Acked-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@9942 a0bf4364-ded3-4de4-8d8a-66a801d63aff