What would it take for Justin Smith to get in the Hall of Fame?

Earlier today, I received this tweet:

@NinersNation Justin Smith will retire a 49er now, is he a first ballot HOF'er?

— ᏣᎾᎡᎬᎽ (@5tevens) June 21, 2013

I think the bigger question is just "Is Justin Smith a HOF'er?" Plenty of 49ers fans will say that he is most definitely a Hall of Famer, but I don't think it's any kind of lock that he gets into the Hall of Fame. I do think he is Hall of Fame caliber. He's one of the most dominant defensive linemen in the game. Last winter we saw just how important he was to the 49ers defense, given the 49ers defensive struggles after he got hurt.

The problem would be how long it took for him to really get his due. He has always been a good defensive lineman, but it seems like he took his game to another level when he came to San Francisco. Will people look at him as a guy who was dominant for a stretch, but won't view it as long enough? I would hope not, but it's hard to read the mind of Hall voters.

When I think of the Hall of Fame, I think of a guy who was considered in the small class of the best at what he did during a given stretch. I don't know how long that stretch of time needs to be, but I do know that Justin Smith has been as good as they come with the 49ers. The stats never showed his dominance, but it was there. Even when he wasn't getting sacks or tackles, he was getting pressure, he was drawing double teams, or opponents were game-planning away from his side of the field.

There was a good article a couple days ago in a Missouri newspaper. They were wondering this very question, and had some good quotations about Smith. This one said it all:

Last year, 49ers radio analyst and former cornerback Eric Davis described to me a scene he watched unfold during the team's bye week in 2011, on a brisk October morning at the team facility.

"Most of the players aren't around," Davis said. "You go outside to where the outdoor weight equipment is set up. It's a cold morning. And through the fog and the mist you see this one character out there. Of course, it's Cowboy. He's blowing steam like a Brahma bull. Just getting in his workout. He won't stop. That's just how he is, and that's how he is on the field. He's relentless."

Realistically I think even without a Super Bowl ring, he's a Hall of Fame football player. How many players have been named All Pro at two different positions in multiple years? He has so physically dominated opposing offensive lines, it has reached almost epic levels the last couple years. But is it enough to get the votes needed to get into the Hall of Fame?