nixos/doc: update the status of Intel Graphics with fixed intel driver

xf86-video-intel is now working again due to a bug fix in Mesa. So this
re-introduces the section on the intel driver and screen-tearing while
discouraging its use generally.

Author: Tim Keller

nixos/doc/manual/configuration/x-windows.chapter.md

@@ -123,27 +123,47 @@ setting](https://en.wikipedia.org/wiki/Mode_setting) (KMS) mechanism, it
 supports Glamor (2D graphics acceleration via OpenGL) and is actively
 maintained, it may perform worse in some cases (like in old chipsets).
 
+There is a second driver, `intel` (provided by the xf86-video-intel package),
+specific to older Intel iGPUs from generation 2 to 9. It is not recommended by
+most distributions: it lacks several modern features (for example, it doesn't
+support Glamor) and the package hasn't been officially updated since 2015.
+
+Third generation and older iGPUs (15-20+ years old) are not supported by the
+`modesetting` driver (X will crash upon startup). Thus, the `intel` driver is
+required for these chipsets.
+Otherwise, the results vary depending on the hardware, so you may have to try
+both drivers. Use the option
+[](#opt-services.xserver.videoDrivers)
+to set one. The recommended configuration for modern systems is:
+
+```nix
+{
+  services.xserver.videoDrivers = [ "modesetting" ];
+}
+```
 ::: {.note}
 The `modesetting` driver doesn't currently provide a `TearFree` option (this
 will become available in an upcoming X.org release), So, without using a
 compositor (for example, see [](#opt-services.picom.enable)) you will
 experience screen tearing.
 :::
 
-There also used to be a second driver, `intel` (provided by the
-xf86-video-intel package), specific to older Intel iGPUs from generation 2 to
-9.
-This driver hasn't been maintained in years and was removed in NixOS 24.11
-after it stopped working. If you chipset is too old to be supported by
-`modesetting` and have no other choice you may try an unsupported NixOS version
-(reportedly working up to NixOS 24.05) and set
+If you experience screen tearing no matter what, this configuration was
+reported to resolve the issue:
 
 ```nix
 {
   services.xserver.videoDrivers = [ "intel" ];
+  services.xserver.deviceSection = ''
+    Option "DRI" "2"
+    Option "TearFree" "true"
+  '';
 }
 ```
 
+Note that this will likely downgrade the performance compared to
+`modesetting` or `intel` with DRI 3 (default).
+
 ## Proprietary NVIDIA drivers {#sec-x11-graphics-cards-nvidia}
 
 NVIDIA provides a proprietary driver for its graphics cards that has

nixos/doc/manual/release-notes/rl-2411.section.md

@@ -231,9 +231,6 @@
 
 - The NVIDIA driver no longer defaults to the proprietary kernel module with versions >= 560. You will need to manually set `hardware.nvidia.open` to select the proprietary or open modules.
 
-- The `intel` driver for the X server (`services.xserver.videoDrives = [ "intel" ]`) is no longer functional due to incompatibilities with the latest Mesa version.
-  All users are strongly encouraged to switch to the generic `modesetting` driver (the default one) whenever possible, for more information see the manual chapter on [Intel Graphics](#sec-x11--graphics-cards-intel) and issue [#342763](https://github.com/NixOS/nixpkgs/issues/342763).
-
 - The `(buildPythonPackage { ... }).override` and `(buildPythonPackage { ... }).overrideDerivation` attributes is now deprecated and removed in favour of `overridePythonAttrs` and `lib.overrideDerivation`.
   This change does not affect the override interface of most Python packages, as [`<pkg>.override`](https://nixos.org/manual/nixpkgs/unstable/#sec-pkg-override) provided by `callPackage` shadows such a locally-defined `override` attribute.
   The `<pkg>.overrideDerivation` attribute of Python packages called with `callPackage` will also remain available after this change.