Binding directions limitation

[Ashish Raniwala]

Hi Guys,
I remember reading limitations of binding directions somewhere but not able to 
find it now. 
I am facing problem with 'in' direction and parameter does not get parameter 
value during component rendering.
Changing to direction auto works fine. 
Can anyone please point me to some resource where I can read about limitations 
on binding directions?
Thanks in advance.
Regards,
Ashish