How to properly wait for transaction completion?

[Vincent DEFERT <vincent.defert%posteo.net@localhost>]

Hi,

I'm working on an I2C driver for the ODROID C2 and I wonder how I should 
do to detect the end of a transaction.
Ideally, once the transaction is started, I'd like to wait in my exec() 
function for a "signal" raised by the interrupt handler, so as to avoid 
a busy wait.
Is this the correct approach? Which API should I use?

Vincent