View source for Lenovo ThinkPad T420

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[[Category:Lenovo (English)]]
This article covers the installation and configuration of Arch Linux on a Lenovo T420 laptop.

== Installation ==
This laptop supports [[Unified_Extensible_Firmware_Interface|UEFI]] as well as the traditional BIOS.

There are no issues with installing Arch Linux with the latest [https://www.archlinux.org/download/ Archiso].

The rest of the installation process can be followed with the [[Official_Arch_Linux_Install_Guide|official install guide]].

== Hardware ==
All hardware not listed below works out-of-the-box.

=== Webcam ===
The integrated [[Webcam_Setup|webcam]] uses the {{ic|uvcvideo}} module which should load automatically. If not, add it to the {{ic|MODULES}} array in {{ic|/etc/[[rc.conf]]}}.

=== FingerPrint Reader ===
FingerPrint reader works great with fprint and PAM (installation of fingerprint-gui recommended).

See [[Fprint#Setup_fingerprint-gui]] for more information.

=== Untested ===
* eSATA
* Firewire

== Laptop Settings ==
=== ACPI ===
[[ACPI_modules|ACPI]] is well supported here. No obvious troubleshoots.

=== Tp_smapi ===
Unfortunately, [[Tp_smapi|tp_smapi]] is only partially supported on the Thinkpad T420. A number of features work since version 0.41. For example, the hard drive protection mechanism [[HDAPS]] now works well. See the linked wiki entry.

Some features like setting the starting threshold for charging the battery do not yet work. To control the battery charging thresholds, install the Perl script {{AUR|tpacpi-bat}} from the [[Arch User Repository|AUR]].

Insert the {{ic|acpi_call}} kernel module by running
 modprobe acpi_call
or by adding it to the {{ic|MODULES}} array in {{ic|/etc/[[rc.conf]]}}.

Manually set the thresholds by calling
 perl /usr/lib/perl5/vendor_perl/tpacpi-bat -v startChargeThreshold 0 40
 perl /usr/lib/perl5/vendor_perl/tpacpi-bat -v stopChargeThreshold 0 80
The example values 40 and 80 given here are in percent of the full battery capacity. Adjust them to your own needs. You may also want to add these lines to {{ic|/etc/rc.local}} to set them at startup. While these values should be permanent, they will be reset any time the battery is removed.

Also, if you are dual booting with Windows, you can still control the battery charging thresholds with Lenovo's Power Manager which communicates directly to the battery controller.

=== CPU Frequency Scaling ===
[[CPU Frequency Scaling|CPU frequency scaling]] is fully supported with all of the available processor models with this laptop.

=== Laptop Mode Tools ===
No significant issues were found using [[Laptop Mode Tools]].

=== PM-Utils ===
Suspending and hibernating with [[Pm-utils|pm-utils]] works as intended.

=== Synaptics ===
TouchPad and TrackPoint do work out of the box, but the TouchPad is way too sensitive (i.e. fast) to be usable, since it is recognized as a mouse. To fix this, [[pacman|install]] the {{Pkg|xf86-input-synaptics}} package and add the following two files to your {{ic|/etc/X11/xorg.conf.d/}} directory:

{{hc|50-thinkpad-trackpoint.conf|<nowiki>
 Section "InputClass"
        Identifier      "ThinkPad TrackPoint"
        MatchProduct    "TPPS/2 IBM TrackPoint"
        MatchDevicePath "/dev/input/event*"
        Option          "EmulateWheel"          "true"
        Option          "EmulateWheelButton"    "2"
        Option          "XAxisMapping"          "6 7"
        Option          "YAxisMapping"          "4 5"
 EndSection
</nowiki>}}

{{hc|50-twofingerscroll.conf|<nowiki>
 Section "InputClass"
        Identifier      "two finger scrolling"
        Driver          "synaptics"
        MatchProduct    "SynPS/2 Synaptics TouchPad"
        MatchDevicePath "/dev/input/event*"
        Option          "VertTwoFingerScroll"   "on"
        Option          "HorizTwoFingerScroll"  "on"
        Option          "EmulateTwoFingerMinW"  "8"
        Option          "EmulateTwoFingerMinZ"  "40"
        Option          "TapButton1"            "1"
 EndSection
</nowiki>}}

Adjust to your own needs. Read [[Touchpad_Synaptics]] for more information.

== Troubleshoots ==
=== Media Keys ===
Media keys that work out of the box:
* Wireless On/Off
* Backlight Brightness settings
* Thinklight
* Mute

You must find a workaround and bind the keys yourself for the rest of them.

=== Rebind Forward and Back keys ===
Keys forward and back (next to cursor keys) can be easily remapped to PageDown/PageUp.

[[pacman|Install]] xmodmap with the package {{Pkg|xorg-server-utils}}

Create a {{ic|~/.Xmodmap}} file with content:
 keysym XF86Back = Page_Up
 keysym XF86Forward = Page_Down

Add this line to your {{ic|~/.xinitrc}} to make it work:
 xmodmap ~/.Xmodmap

You can also re-map AudioPrev ({{Keypress|Fn+Left}}) and AudioNext ({{Keypress|Fn+Right}}) to Home/End:
 keysym XF86AudioNext = End
 keysym XF86AudioPrev = Home

{{Note|You have to log out for the changes to take effect.}}

{{Note|The keys should work out of the box, at least on [[KDE]].}}

=== Shutdown on Battery ===
One user has reported that his T420 was rebooting on shutdown on battery power. This was fixed by disabling the module {{ic|ehci_hcd}}. See [[Kernel_modules#Blacklisting]] for more information.

=== Hang on Reboot ===
This is a problem on many laptops and can be fixed by [[Kernel modules#Blacklisting|blacklisting]] the {{ic|e1000e}} kernel module.

=== No Backlight Controls ===
One user has reported that the brightness controls (fn+home, fn+end) did not work in some desktop environments. This could be fixed by adding the following kernel modules to /boot/grub/menu.lst.
acpi_backlight=vendor acpi_osi=Linux