You can charge and do many more with
ideviceinstaller.
In fact, I have the impression that you only need to run usbmuxd, already installed on slackware.
I charge all my iOS devices with the computer (less current to charge, better health for the battery)
You just need to make sure that usbmuxd is running after you plug the device. If it's not running on phones you will have even slower charge and on iPads I think there is no charging (not sure)
You can have backups (I never tried restore), statistics about battery health/life, install programs.