Can someone provide a definitive description of the parameters taken by dev_attach()?

There are several posts in this forum that have asked this question going back to 2009 but no clear answer that I can 
find.

In particular, what does dev_attach() do with the 5th, 6th parameters? What are the expected values and how/when are 
they updated by dev_attach(). 

How is the 7th parameter used?

Thanks,
John