A complete smartgun system really has three parts:
(1) A smartgun for the weapon, either internal or external.
(2) A smartlink for the user, either implanted or worn (required for accuracy and dice pool modifiers).
(3) A direct neural interface between the weapon and the user (required for mental commands, e.g., change modes or eject a clip with a Free Action instead of a Simple Action)
The following reasoning goes a little beyond the basic description of a smartgun system (SR5 p.433), but bear with me a minute: A smartlink with no DNI is just a better laser sight; you get the accuracy bonus but can't send mental commands to the weapon. With a DNI but no smartlink, you could still command the weapon (Free Actions instead of Simple Actions), but wouldn't get the accuracy benefit. You need both the DNI and smartlink, plus a wireless Matrix connection, to gain the dice pool bonus ... +2 if you paid Essence (p.453) or +1 if you didn't (p.444). For a weak explanation of why the Matrix helps you shoot better, see "Wireless Functionality" (p.420) and "Wireless Bonuses" (p.421).
If a technomancer can access the Matrix with only their living persona, then they have the equivalent of a wetware datajack in their brain, which is good for the DNI requirement. They can interface with wireless devices (p.249). They could establish a non-wireless connection with the skinlink echo (Data Trails p.59) if they have it. With a smartgun accessory installed in their weapon, they can give mental commands as Free Actions. With a smartlink enhancement installed in glasses or contact lenses, they also qualify for the +2 Accuracy and +1 dice pool. But they can't get the +2 dice pool without paying Essence for the smartlink.