I don't see this as being a very good trade.
CK, I see where you're coming from with Fitzgerald's injury, but IMO they still have Boldin, Bryant Johnson and probably some filler guys who can do an okay-enough job. Davis is the last legs of that god awful offensive line.
As for the Raiders -- obviously they want to rid themselves of Porter, so I guess any trade is a win for them, but Davis? They have invested a mega-load contract in a LT already in Robert Gallery and although their line is agiging, they have a lot of younger potential on the team that will be a lot cheaper and fortuitious in the long-term.
Of course, this is the two numbskull franchises of the NFL, so logic and the long-term planning are about as present as two vegetarians in a meat market.