nixos/xserver: use modern video drivers

cirrus is obsolete: https://www.vintage3d.org/cirrus.php
nv is obsolete: https://www.phoronix.com/scan.php?page=article&item=nvidia_kills_nv&num=1
vesa is obsolete: https://www.phoronix.com/scan.php?page=news_item&px=Nzc3Nw
ati and ati_unfree are superseded by amdgpu and amdgpu-pro: https://wiki.gentoo.org/wiki/ATI_FAQ#Is_my_AMD.2FATI_board_supported.3F
nouveau and fbdev added for better fallback support.

nixos/doc/manual/configuration/x-windows.xml

@@ -150,7 +150,6 @@
 <xref linkend="opt-services.xserver.videoDrivers"/> = [ "nvidiaLegacy390" ];
 <xref linkend="opt-services.xserver.videoDrivers"/> = [ "nvidiaLegacy340" ];
 <xref linkend="opt-services.xserver.videoDrivers"/> = [ "nvidiaLegacy304" ];
-<xref linkend="opt-services.xserver.videoDrivers"/> = [ "nvidiaLegacy173" ];
 </programlisting>
    You may need to reboot after enabling this driver to prevent a clash with
    other kernel modules.
@@ -159,21 +158,16 @@
  <simplesect xml:id="sec-x11--graphics-cards-amd">
   <title>Proprietary AMD drivers</title>
   <para>
-   AMD provides a proprietary driver for its graphics cards that has better 3D
-   performance than the X.org drivers. It is not enabled by default because
-   it’s not free software. You can enable it as follows:
+   AMD provides a proprietary driver for its graphics cards that is not
+   enabled by default because it’s not Free Software, is often broken
+   in nixpkgs and as of this writing doesn't offer more features or
+   performance. If you still want to use it anyway, you need to explicitly set:
 <programlisting>
-<xref linkend="opt-services.xserver.videoDrivers"/> = [ "ati_unfree" ];
+<xref linkend="opt-services.xserver.videoDrivers"/> = [ "amdgpu-pro" ];
 </programlisting>
    You will need to reboot after enabling this driver to prevent a clash with
    other kernel modules.
   </para>
-  <note>
-  <para>
-   For recent AMD GPUs you most likely want to keep either the defaults
-   or <literal>"amdgpu"</literal> (both free).
-  </para>
-  </note>
  </simplesect>
  <simplesect xml:id="sec-x11-touchpads">
   <title>Touchpads</title>

nixos/doc/manual/release-notes/rl-2105.xml

@@ -539,6 +539,11 @@ self: super:
      <package>imagemagick6Big</package> if you need the older version.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     <xref linkend="opt-services.xserver.videoDrivers" /> no longer uses the deprecated <literal>cirrus</literal> and <literal>vesa</literal> device dependent X drivers by default. It also enables both <literal>amdgpu</literal> and <literal>nouveau</literal> drivers by default now.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 

nixos/modules/services/x11/xserver.nix

@@ -251,11 +251,10 @@ in
 
       videoDrivers = mkOption {
         type = types.listOf types.str;
-        # !!! We'd like "nv" here, but it segfaults the X server.
-        default = [ "radeon" "cirrus" "vesa" "modesetting" ];
+        default = [ "amdgpu" "radeon" "nouveau" "modesetting" "fbdev" ];
         example = [
-          "ati_unfree" "amdgpu" "amdgpu-pro"
-          "nv" "nvidia" "nvidiaLegacy390" "nvidiaLegacy340" "nvidiaLegacy304"
+          "nvidia" "nvidiaLegacy390" "nvidiaLegacy340" "nvidiaLegacy304"
+          "amdgpu-pro"
         ];
         # TODO(@oxij): think how to easily add the rest, like those nvidia things
         relatedPackages = concatLists