Determine which graphics driver Xorg uses

You can check the Xorg startup log file, usually /var/log/Xorg.0.log and look at which modules it is loading. By default Xorg can try to autodetect but you can manually force a driver by putting a Device stanza in an Xorg conf file. Here is what the Xorg startup log will look like for an nvidia card and the nvidia proprietary driver.

[  3702.470] (II) xfree86: Adding drm device (/dev/dri/card0)
[  3702.472] (--) PCI:*(0:3:0:0) 10de:1184:3842:3774 rev 161, Mem @ 0xfa000000/16777216, 0xd8000000/134217728, 0xd6000000/33554432, I/O @ 0x0000cc00/128, BIOS @ 0x????????/524288
[  3702.472] (II) LoadModule: "glx"
[  3702.473] (II) Loading /usr/lib64/opengl/nvidia/extensions/libglx.so
[  3702.476] (II) Module glx: vendor="NVIDIA Corporation"
[  3702.476]    compiled for 4.0.2, module version = 1.0.0
[  3702.476]    Module class: X.Org Server Extension
[  3702.476] (II) NVIDIA GLX Module  355.11  Wed Aug 26 16:02:11 PDT 2015
[  3702.476] (II) LoadModule: "nvidia"
[  3702.476] (II) Loading /usr/lib64/xorg/modules/drivers/nvidia_drv.so
[  3702.476] (II) Module nvidia: vendor="NVIDIA Corporation"
[  3702.476]    compiled for 4.0.2, module version = 1.0.0
[  3702.476]    Module class: X.Org Video Driver
[  3702.476] (II) NVIDIA dlloader X Driver  355.11  Wed Aug 26 15:38:55 PDT 2015
[  3702.476] (II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
[  3702.476] (++) using VT number 7

One solution that I have found is to check what drivers are actually loaded while X is running. On my system, the drivers are installed under

• /usr/lib/xorg/modules/drivers/
• /usr/lib/x86_64-linux-gnu/nvidia/xorg/

so I can check what is currently loaded with

sudo lsof +D /usr/lib/xorg/modules/drivers/ +D /usr/lib/x86_64-linux-gnu/nvidia/xorg/

Right now I get

COMMAND  PID USER  FD   TYPE DEVICE SIZE/OFF   NODE NAME
Xorg    4473 root mem    REG  253,0    90360 536108 /usr/lib/xorg/modules/drivers/modesetting_drv.so

so I guess I'm using the modesetting driver.

Here's an attempt to automatize the analysis of the log:

#!/bin/bash

if [ -z "$1" ]; then
    logfile=/var/log/Xorg.0.log
else
    logfile="$1"
fi

sed -n 's@.* Loading .*/\(.*\)_drv.so@\1@p' "$logfile" |
    while read driver; do
        if ! grep -q "Unloading $driver" "$logfile"; then
            echo $driver
            break
        fi
    done

Any ideas how to make it simpler are welcome. Ideally I'd like to have a direct solution — by a query to Xorg instead of parsing its logs.