If the brightness control hotkeys are not working in your HP Envy TouchSmart 17 after windows 10 update even though the device manager in display adapters are properly updated, then try the following solution:
Product Name: HP ENVY TouchSmart 17-j140us N
Operating System: Microsoft Windows 10 (64-bit)
Download and reinstall the Chipset driver on the link given at the bottom.
When this has completed, do not restart as prompted, instead download and reinstall the Intel HD Graphics driver on the link below at the bottom.
When this has completed, shutdown the notebook.
Unplug the AC Adapter and then remove the battery. Hold down the Power button for 30 seconds. Re-insert the battery and plug in the AC Adapter.
Tap away at the esc key as you start the notebook to launch the Start-up Menu and then select f10 to enter the bios menu. Press f9 to load the defaults ( this is sometimes f5, but the menu at the bottom will show the correct key ), use the arrow keys to select 'Yes' and hit enter. Press f10 to save the setting and again use the arrow keys to select 'Yes' and hit enter.