Dwarf stonecunning - active or passive search

[Bobsayshello]

Is the stonecunning search a dwarf automatically performs an active search or a passive one?

If a dwarf enters a room and walks a circuit, 10ft by any stone structure, he has the ability to check for any unusual stonework.

The DM should be determining if the dwarf detects anything, otherwise when the player is told to make a roll he knows something is there (or else he is rolling constantly which delays the game considerably).

My question is does the dwarf 'take 10' since he isn't actively searching (so 10 +2 +Perception) or does he do a d20 roll to determine if he finds anything (d20 +2 +Perception). Also if he then is doing a d20 roll then does the time it takes to find/not find anything that of a passive search or an active one?

[Mauril]

Ideally, it should be a roll done in secret by the GM using the full perception bonus of the dwarven character. It is a passive search, where the dwarf knows if he notices something, but does not know if he doesn't notice something.