Check which display driver is running in Linux

[root@localhost ~]# lspci -nnk | grep -i vga -A3 | grep 'in use'
Kernel driver in use: nvidia

lspci 

-nn Show PCI vendor and device codes as both numbers and names

-k Show kernel drivers handling each device and also kernel modules capable of handling it. 

grep

-i include vga line

-A3 show the 3 lines after match, which shows the driver loaded line

'in use' show the line that has the in use status