Thanks for clarifying and expanding.

One of the reasons for my own original investigation was to understand how one might maximize iPhone charge speed when connected to a computer via a powered USB hub.

Even when the USB hub is connected to a modern Mac which itself could support and negotiate the fast 1amp charging of a directly connected iPhone, when connected through the powered hub the iPhone seems to limit itself to the more pedestrian 500ma charge rate.

Many USB hubs have power supplies that can deliver more than 500ma in aggregate, but I didn't find anything in the Mac or iPhone characteristics that would allow the iPhone to negotiate and draw the additional power from a USB hub.

As far as I know Apple does not sell a simple USB hub of any kind that might support the 1amp or 2amp charge rates. I don't know whether the USB ports on something like the Thunderbolt display can do it, but that would be a $1000 hub!

Must an iPhone or iPad be directly connected to a Mac in order to utilize the higher charging rates? Or is there a way to do so through a (very up to date) USB hub?

Problem illustration: I have (among others) a 2011 MacBook Air which has exactly two USB ports. I also have an iPhone and iPad. If I connect each directly to the computer then I have zero USB ports for anything else.

If I attach a USB hub then any iDevices connected through the hub charge much more slowly. The iPad actually slowly discharges if the screen is on while hub connected since the minimum current to support in-use iPad charging is 1amp.