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131 lines
4.5 KiB
Markdown
131 lines
4.5 KiB
Markdown
# Customizing display configuration {#module-hardware-display}
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This section describes how to customize display configuration using:
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- kernel modes
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- EDID files
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Example situations it can help you with:
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- display controllers (external hardware) not advertising EDID at all,
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- misbehaving graphics drivers,
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- loading custom display configuration before the Display Manager is running,
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## Forcing display modes {#module-hardware-display-modes}
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In case of very wrong monitor controller and/or video driver combination you can
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[force the display to be enabled](https://mjmwired.net/kernel/Documentation/fb/modedb.txt#41)
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and skip some driver-side checks by adding `video=<OUTPUT>:e` to `boot.kernelParams`.
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This is exactly the case with [`amdgpu` drivers](https://gitlab.freedesktop.org/drm/amd/-/issues/615#note_1987392)
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```nix
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{
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# force enabled output to skip `amdgpu` checks
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hardware.display.outputs."DP-1".mode = "e";
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# completely disable output no matter what is connected to it
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hardware.display.outputs."VGA-2".mode = "d";
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/* equals
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boot.kernelParams = [ "video=DP-1:e" "video=VGA-2:d" ];
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*/
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}
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```
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## Crafting custom EDID files {#module-hardware-display-edid-custom}
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To make custom EDID binaries discoverable you should first create a derivation storing them at
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`$out/lib/firmware/edid/` and secondly add that derivation to `hardware.display.edid.packages` NixOS option:
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```nix
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{
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hardware.display.edid.packages = [
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(pkgs.runCommand "edid-custom" {} ''
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mkdir -p $out/lib/firmware/edid
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base64 -d > "$out/lib/firmware/edid/custom1.bin" <<'EOF'
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<insert your base64 encoded EDID file here `base64 < /sys/class/drm/card0-.../edid`>
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EOF
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base64 -d > "$out/lib/firmware/edid/custom2.bin" <<'EOF'
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<insert your base64 encoded EDID file here `base64 < /sys/class/drm/card1-.../edid`>
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EOF
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'')
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];
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}
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```
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There are 2 options significantly easing preparation of EDID files:
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- `hardware.display.edid.linuxhw`
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- `hardware.display.edid.modelines`
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## Assigning EDID files to displays {#module-hardware-display-edid-assign}
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To assign available custom EDID binaries to your monitor (video output) use `hardware.display.outputs."<NAME>".edid` option.
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Under the hood it adds `drm.edid_firmware` entry to `boot.kernelParams` NixOS option for each configured output:
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```nix
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{
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hardware.display.outputs."VGA-1".edid = "custom1.bin";
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hardware.display.outputs."VGA-2".edid = "custom2.bin";
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/* equals:
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boot.kernelParams = [ "drm.edid_firmware=VGA-1:edid/custom1.bin,VGA-2:edid/custom2.bin" ];
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*/
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}
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```
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## Pulling files from linuxhw/EDID database {#module-hardware-display-edid-linuxhw}
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`hardware.display.edid.linuxhw` utilizes `pkgs.linuxhw-edid-fetcher` to extract EDID files
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from https://github.com/linuxhw/EDID based on simple string/regexp search identifying exact entries:
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```nix
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{
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hardware.display.edid.linuxhw."PG278Q_2014" = [ "PG278Q" "2014" ];
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/* equals:
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hardware.display.edid.packages = [
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(pkgs.linuxhw-edid-fetcher.override {
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displays = {
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"PG278Q_2014" = [ "PG278Q" "2014" ];
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};
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})
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];
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*/
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}
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```
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## Using XFree86 Modeline definitions {#module-hardware-display-edid-modelines}
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`hardware.display.edid.modelines` utilizes `pkgs.edid-generator` package allowing you to
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conveniently use [`XFree86 Modeline`](https://en.wikipedia.org/wiki/XFree86_Modeline) entries as EDID binaries:
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```nix
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{
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hardware.display.edid.modelines."PG278Q_60" = " 241.50 2560 2608 2640 2720 1440 1443 1448 1481 -hsync +vsync";
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hardware.display.edid.modelines."PG278Q_120" = " 497.75 2560 2608 2640 2720 1440 1443 1448 1525 +hsync -vsync";
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/* equals:
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hardware.display.edid.packages = [
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(pkgs.edid-generator.overrideAttrs {
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clean = true;
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modelines = ''
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Modeline "PG278Q_60" 241.50 2560 2608 2640 2720 1440 1443 1448 1481 -hsync +vsync
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Modeline "PG278Q_120" 497.75 2560 2608 2640 2720 1440 1443 1448 1525 +hsync -vsync
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'';
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})
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];
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*/
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}
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```
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## Complete example for Asus PG278Q {#module-hardware-display-pg278q}
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And finally this is a complete working example for a 2014 (first) batch of [Asus PG278Q monitor with `amdgpu` drivers](https://gitlab.freedesktop.org/drm/amd/-/issues/615#note_1987392):
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```nix
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{
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hardware.display.edid.modelines."PG278Q_60" = " 241.50 2560 2608 2640 2720 1440 1443 1448 1481 -hsync +vsync";
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hardware.display.edid.modelines."PG278Q_120" = " 497.75 2560 2608 2640 2720 1440 1443 1448 1525 +hsync -vsync";
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hardware.display.outputs."DP-1".edid = "PG278Q_60.bin";
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hardware.display.outputs."DP-1".mode = "e";
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}
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```
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