Nixpkgs: ALPS TouchPad in absolute mode

[Zimmi48]

Issue description

I'm having the same issue as is described on this forum: https://bbs.archlinux.org/viewtopic.php?id=40141
When I put my finger somewhere on the touchpad, the cursor moves to the corresponding absolute position on the screen.

Steps to reproduce

I am not sure that this is reproducible because I don't have this problem with the installation image booted from a USB key.
The problem also disappears sometimes after I used an external mouse long enough.

Technical details

• System: NixOS 16.09
• Nix version: 1.11.4
• Nixpkgs version: 16.09.733.246c937

The output of xinput is

⎡ Virtual core pointer                      id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ HID 413c:8158                             id=10   [slave  pointer  (2)]
⎜   ↳ AlpsPS/2 ALPS DualPoint TouchPad          id=13   [slave  pointer  (2)]
⎜   ↳ AlpsPS/2 ALPS DualPoint Stick             id=14   [slave  pointer  (2)]
⎣ Virtual core keyboard                     id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
    ↳ Video Bus                                 id=6    [slave  keyboard (3)]
    ↳ Power Button                              id=7    [slave  keyboard (3)]
    ↳ Sleep Button                              id=8    [slave  keyboard (3)]
    ↳ HID 413c:8157                             id=9    [slave  keyboard (3)]
    ↳ Laptop_Integrated_Webcam_0.3M             id=11   [slave  keyboard (3)]
    ↳ AT Translated Set 2 keyboard              id=12   [slave  keyboard (3)]
    ↳ Dell WMI hotkeys                          id=15   [slave  keyboard (3)]

The output of dmesg | grep Synaptics is void. The output of dmesg | grep ALPS is

[   19.914892] input: AlpsPS/2 ALPS DualPoint Stick as /devices/platform/i8042/serio1/input/input16
[   19.932817] input: AlpsPS/2 ALPS DualPoint TouchPad as /devices/platform/i8042/serio1/input/input13

My hardware-configuration.nix is:

{ config, lib, pkgs, ... }:

{
  imports =
    [ <nixpkgs/nixos/modules/installer/scan/not-detected.nix>
    ];

  boot.initrd.availableKernelModules = [ "uhci_hcd" "ehci_pci" "ahci" "firewire_ohci" "usbhid" "usb_storage" "sd_mod" "sr_mod" "sdhci_pci" ];
  boot.kernelModules = [ "kvm-intel" ];
  boot.extraModulePackages = [ ];

  fileSystems."/" =
    { device = "/dev/disk/by-uuid/245c8490-4e85-4836-aa1a-13a3fc9d94c3";
      fsType = "ext4";
    };

  fileSystems."/home" =
    { device = "/dev/disk/by-uuid/c464e14f-1002-4828-8859-a55766355b9c";
      fsType = "ext4";
    };

  swapDevices =
    [ { device = "/dev/disk/by-uuid/36b77ea3-bb39-4458-92cf-374308ff52d4"; }
    ];

  nix.maxJobs = lib.mkDefault 2;
}

[sid-kap]

I don't know why this works, but for me adding

services.synaptics.enable = true;

fixed the problem.

[Zimmi48]

I think you mean

services.xserver.synaptics.enable = true;

It fixed the problem for me too. If this option is needed for touchpads, I don't get why it isn't proposed in the default configuration.nix file.

[Zimmi48]

I'll leave it to someone else to take the decision whether to close this issue or to leave it open. The problem is fixed for me but it still feels like it is a bad user experience that could be solved by improving the default configuration.nix file which is proposed to new users.

[vcunat]

I suspect the intention was not to include the driver for those who don't need it. Still, the savings are probably very small.

[dezgeg]

I have one laptop affected by this, IIRC it affects the install ISOs as well. Sufficiently annoying such that we really should figure this one out for 17.03.

[dezgeg]

I guess we can just set services.xserver.libinput.enable = true; by default. According to Arch wiki, the synaptics driver is deprecated / not updated anymore.

[vcunat]

Last xf86-input-synaptics release was in November 2016, but I don't know developer plans. Maybe X is getting deprecated already :-)