Try this:
Go to controller's monitor page (listing the APs connected to that controller)
Select the 'modify devices' above the list table
'Select all' from the bottom of the table
Run report
Either choose 'client session' or 'custom' report type (if custom, expand options under client session report)
Choose session data by 'device type' (other good bits are by OS, manufacturer, and model)
- I recommend doing a once over with all the options selected, then you can pick and choose which are useful to you. The above are just what I image would fit your objective
- Once you've got the right pieces, you can do the same steps and then set it to repeat using the report scheduling portion in the report definition
*Note* - from the method I chose to select devices for reporting, the above report would be excluding clients directly connected to the controller by-passing APs (if there are any)