We had one job that required installing a privacey fence with gates at a daycare to close in the kiddie pool as per state regulation. I called a local fab company and had them built custom posts that they welded to a 6x6 steel plate and it had 4- 3/8" holes drilled in them.
This job used vinyl fence panels for everything so when I speced them out I took a peice of the vinyl post sleeve cover so they could get/use a piece of steel tubing as close to the ID of the post sleeve as possible.
Anyhow, used 3/8"x6" redhead anchors to anchor each post to the concrete. (posts were all primed and painted with epoxy prior installation) and used SS washers under the post plate base to level then up. Slid the post sleeves oer them, and marked/drilled SS screws through the brackets that hold the fence panels in place. Took alot of tinker time to put it all in place, but the state actually took pictures of what we did and now uses it in their pamplets they hand out to daycare providers as to what they are looking for when a daycare decided to incorporate a pool.
Problem with hanging a gate in a situation like above, even using a steel post, depending on size of gate and finish material, there will be alot of weight, most of it pulling on the top half of the post...which will make it naturally want to sag. This is why gate posts are always done a little deeper hole wise, and typically larger material when compared to line posts that see nothing but shear load persay.
You can try to do the steel post redhead bolted to the driveway and hiding it with a finished material, or a easy solution would be rent a core drill and drill a hole through the driveway and down to footing depth, and put a standard wood post in, that way it will be ridgid enough it will support the weight of the gate/s.
