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nixos/device-tree: improve overlays support
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Now allows applying external overlays either in form of
.dts file, literal dts context added to store or precompiled .dtbo.

If overlays are defined, kernel device-trees are compiled with '-@'
so the .dtb files contain symbols which we can reference in our
overlays.

Since `fdtoverlay` doesn't respect `/ compatible` by itself
we query compatible strings of both `dtb` and `dtbo(verlay)`
and apply only if latter is substring of the former.

Also adds support for filtering .dtb files (as there are now nearly 1k
dtbs).

Co-authored-by: georgewhewell <georgerw@gmail.com>
Co-authored-by: Kai Wohlfahrt <kai.wohlfahrt@gmail.com>
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@sorki @georgewhewell @kwohlfahrt
3 people committed Sep 9, 2020
1 parent 51428e8 commit 6c9df40
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11 changes: 11 additions & 0 deletions nixos/doc/manual/release-notes/rl-2009.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -833,6 +833,17 @@ CREATE ROLE postgres LOGIN SUPERUSER;
of the default <literal>out</literal> output anymore - if you relied on the
<literal>notmuch-emacs-mua</literal> binary or the emacs lisp files, access them via
the <literal>notmuch.emacs</literal> output.

Device tree overlay support was improved in
<link xlink:href="https://github.com/NixOS/nixpkgs/pull/79370">#79370</link>
and now uses <xref linkend="opt-hardware.deviceTree.kernelPackage"/>
instead of <option>hardware.deviceTree.base</option>.

<xref linkend="opt-hardware.deviceTree.overlays"/> configuration was
extended to support <literal>.dts</literal> files with symbols.

Device trees can now be filtered by setting
<xref linkend="opt-hardware.deviceTree.filter"/> option.
</para>
</listitem>
<listitem>
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164 changes: 151 additions & 13 deletions nixos/modules/hardware/device-tree.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,114 @@ with lib;

let
cfg = config.hardware.deviceTree;
in {

overlayType = types.submodule {
options = {
name = mkOption {
type = types.str;
description = ''
Name of this overlay
'';
};

dtsFile = mkOption {
type = types.nullOr types.path;
description = ''
Path to .dts overlay file, overlay is applied to
each .dtb file matching "compatible" of the overlay.
'';
default = null;
example = literalExample "./dts/overlays.dts";
};

dtsText = mkOption {
type = types.nullOr types.str;
default = null;
description = ''
Literal DTS contents, overlay is applied to
each .dtb file matching "compatible" of the overlay.
'';
example = literalExample ''
/dts-v1/;
/plugin/;
/ {
compatible = "raspberrypi";
fragment@0 {
target-path = "/soc";
__overlay__ {
pps {
compatible = "pps-gpio";
status = "okay";
};
};
};
};
'';
};

dtboFile = mkOption {
type = types.nullOr types.path;
default = null;
description = ''
Path to .dtbo compiled overlay file.
'';
};
};
};

# this requires kernel package
dtbsWithSymbols = pkgs.stdenv.mkDerivation {
name = "dtbs-with-symbols";
inherit (cfg.kernelPackage) src nativeBuildInputs depsBuildBuild;
patches = map (patch: patch.patch) cfg.kernelPackage.kernelPatches;
buildPhase = ''
patchShebangs scripts/*
substituteInPlace scripts/Makefile.lib \
--replace 'DTC_FLAGS += $(DTC_FLAGS_$(basetarget))' 'DTC_FLAGS += $(DTC_FLAGS_$(basetarget)) -@'
make ${pkgs.stdenv.hostPlatform.platform.kernelBaseConfig} ARCH="${pkgs.stdenv.hostPlatform.platform.kernelArch}"
make dtbs ARCH="${pkgs.stdenv.hostPlatform.platform.kernelArch}"
'';
installPhase = ''
make dtbs_install INSTALL_DTBS_PATH=$out/dtbs ARCH="${pkgs.stdenv.hostPlatform.platform.kernelArch}"
'';
};

filterDTBs = src: if isNull cfg.filter
then "${src}/dtbs"
else
pkgs.runCommand "dtbs-filtered" {} ''
mkdir -p $out
cd ${src}/dtbs
find . -type f -name '${cfg.filter}' -print0 \
| xargs -0 cp -v --no-preserve=mode --target-directory $out --parents
'';

# Compile single Device Tree overlay source
# file (.dts) into its compiled variant (.dtbo)
compileDTS = name: f: pkgs.callPackage({ dtc }: pkgs.stdenv.mkDerivation {
name = "${name}-dtbo";

nativeBuildInputs = [ dtc ];

buildCommand = ''
dtc -I dts ${f} -O dtb -@ -o $out
'';
}) {};

# Fill in `dtboFile` for each overlay if not set already.
# Existence of one of these is guarded by assertion below
withDTBOs = xs: flip map xs (o: o // { dtboFile =
if isNull o.dtboFile then
if !isNull o.dtsFile then compileDTS o.name o.dtsFile
else compileDTS o.name (pkgs.writeText "dts" o.dtsText)
else o.dtboFile; } );

in
{
imports = [
(mkRemovedOptionModule [ "hardware" "deviceTree" "base" ] "Use hardware.deviceTree.kernelPackage instead")
];

options = {
hardware.deviceTree = {
enable = mkOption {
Expand All @@ -16,13 +123,13 @@ in {
'';
};

base = mkOption {
default = "${config.boot.kernelPackages.kernel}/dtbs";
defaultText = "\${config.boot.kernelPackages.kernel}/dtbs";
example = literalExample "pkgs.device-tree_rpi";
kernelPackage = mkOption {
default = config.boot.kernelPackages.kernel;
defaultText = "config.boot.kernelPackages.kernel";
example = literalExample "pkgs.linux_latest";
type = types.path;
description = ''
The path containing the base device-tree (.dtb) to boot. Contains
Kernel package containing the base device-tree (.dtb) to boot. Uses
device trees bundled with the Linux kernel by default.
'';
};
Expand All @@ -38,14 +145,32 @@ in {
'';
};

filter = mkOption {
type = types.nullOr types.str;
default = null;
example = "*rpi*.dtb";
description = ''
Only include .dtb files matching glob expression.
'';
};

overlays = mkOption {
default = [];
example = literalExample
"[\"\${pkgs.device-tree_rpi.overlays}/w1-gpio.dtbo\"]";
type = types.listOf types.path;
example = literalExample ''
[
{ name = "pps"; dtsFile = ./dts/pps.dts; }
{ name = "spi";
dtsText = "...";
}
{ name = "precompiled"; dtboFile = ./dtbos/example.dtbo; }
]
'';
type = types.listOf (types.coercedTo types.path (path: {
name = baseNameOf path;
dtboFile = path;
}) overlayType);
description = ''
A path containing device tree overlays (.dtbo) to be applied to all
base device-trees.
List of overlays to apply to base device-tree (.dtb) files.
'';
};

Expand All @@ -54,14 +179,27 @@ in {
type = types.nullOr types.path;
internal = true;
description = ''
A path containing the result of applying `overlays` to `base`.
A path containing the result of applying `overlays` to `kernelPackage`.
'';
};
};
};

config = mkIf (cfg.enable) {

assertions = let
invalidOverlay = o: isNull o.dtsFile && isNull o.dtsText && isNull o.dtboFile;
in lib.singleton {
assertion = lib.all (o: !invalidOverlay o) cfg.overlays;
message = ''
deviceTree overlay needs one of dtsFile, dtsText or dtboFile set.
Offending overlay(s):
${toString (map (o: o.name) (builtins.filter invalidOverlay cfg.overlays))}
'';
};

hardware.deviceTree.package = if (cfg.overlays != [])
then pkgs.deviceTree.applyOverlays cfg.base cfg.overlays else cfg.base;
then pkgs.deviceTree.applyOverlays (filterDTBs dtbsWithSymbols) (withDTBOs cfg.overlays)
else (filterDTBs cfg.kernelPackage);
};
}
27 changes: 21 additions & 6 deletions pkgs/os-specific/linux/device-tree/default.nix
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Original file line number Diff line number Diff line change
@@ -1,16 +1,31 @@
{ stdenvNoCC, dtc, findutils }:

with stdenvNoCC.lib; {
applyOverlays = (base: overlays: stdenvNoCC.mkDerivation {
applyOverlays = (base: overlays': stdenvNoCC.mkDerivation {
name = "device-tree-overlays";
nativeBuildInputs = [ dtc findutils ];
buildCommand = let
quotedDtbos = concatMapStringsSep " " (o: "\"${toString o}\"") (toList overlays);
overlays = toList overlays';
in ''
for dtb in $(find ${base} -name "*.dtb" ); do
outDtb=$out/$(realpath --relative-to "${base}" "$dtb")
mkdir -p "$(dirname "$outDtb")"
fdtoverlay -o "$outDtb" -i "$dtb" ${quotedDtbos};
mkdir -p $out
cd ${base}
find . -type f -name '*.dtb' -print0 \
| xargs -0 cp -v --no-preserve=mode --target-directory $out --parents
for dtb in $(find $out -type f -name '*.dtb'); do
dtbCompat="$( fdtget -t s $dtb / compatible )"
${flip (concatMapStringsSep "\n") overlays (o: ''
overlayCompat="$( fdtget -t s ${o.dtboFile} / compatible )"
# overlayCompat in dtbCompat
if [[ "$dtbCompat" =~ "$overlayCompat" ]]; then
echo "Applying overlay ${o.name} to $( basename $dtb )"
mv $dtb{,.in}
fdtoverlay -o "$dtb" -i "$dtb.in" ${o.dtboFile};
rm $dtb.in
fi
'')}
done
'';
});
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