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nixpkgs/nixos/modules/system/boot/kernel_config.nix
Matthieu Coudron 3bb7b3f02e linux: ability to merge structured configs
This should make the composability of kernel configurations more straigthforward.

- now distinguish freeform options from tristate ones
- will look for a structured config in kernelPatches too
one can now access the structuredConfig from a kernel via linux_test.configfile.structuredConfig
in order to reinject it into another kernel, no need to rewrite the config from scratch

The following merge strategies are used in case of conflict:
-- freeform items must be equal or they conflict (mergeEqualOption)
-- for tristate (y/m/n) entries, I use the mergeAnswer strategy which takes the best available value, "best" being defined by the user (by default "y" > "m" > "n", e.g. if one entry is both marked "y" and "n", "y" wins)
-- if one item is both marked optional/mandatory, mandatory wins (mergeFalseByDefault)
2019-01-28 09:06:33 +09:00

138 lines
3.7 KiB
Nix

{ lib, config, ... }:
with lib;
let
findWinner = candidates: winner:
any (x: x == winner) candidates;
# winners is an ordered list where first item wins over 2nd etc
mergeAnswer = winners: locs: defs:
let
values = map (x: x.value) defs;
freeformAnswer = intersectLists values winners;
inter = intersectLists values winners;
winner = head winners;
in
if defs == [] then abort "This case should never happen."
else if winner == [] then abort "Give a valid list of winner"
else if inter == [] then mergeOneOption locs defs
else if findWinner values winner then
winner
else
mergeAnswer (tail winners) locs defs;
mergeFalseByDefault = locs: defs:
if defs == [] then abort "This case should never happen."
else if any (x: x == false) defs then false
else true;
kernelItem = types.submodule {
options = {
tristate = mkOption {
type = types.enum [ "y" "m" "n" null ] // {
merge = mergeAnswer [ "y" "m" "n" ];
};
default = null;
internal = true;
visible = true;
description = ''
Use this field for tristate kernel options expecting a "y" or "m" or "n".
'';
};
freeform = mkOption {
type = types.nullOr types.str // {
merge = mergeEqualOption;
};
default = null;
example = ''MMC_BLOCK_MINORS.freeform = "32";'';
description = ''
Freeform description of a kernel configuration item value.
'';
};
optional = mkOption {
type = types.bool // { merge = mergeFalseByDefault; };
default = false;
description = ''
Wether option should generate a failure when unused.
'';
};
};
};
mkValue = with lib; val:
let
isNumber = c: elem c ["0" "1" "2" "3" "4" "5" "6" "7" "8" "9"];
in
if (val == "") then "\"\""
else if val == "y" || val == "m" || val == "n" then val
else if all isNumber (stringToCharacters val) then val
else if substring 0 2 val == "0x" then val
else val; # FIXME: fix quoting one day
# generate nix intermediate kernel config file of the form
#
# VIRTIO_MMIO m
# VIRTIO_BLK y
# VIRTIO_CONSOLE n
# NET_9P_VIRTIO? y
#
# Borrowed from copumpkin https://github.com/NixOS/nixpkgs/pull/12158
# returns a string, expr should be an attribute set
# Use mkValuePreprocess to preprocess option values, aka mark 'modules' as 'yes' or vice-versa
# use the identity if you don't want to override the configured values
generateNixKConf = exprs:
let
mkConfigLine = key: item:
let
val = if item.freeform != null then item.freeform else item.tristate;
in
if val == null
then ""
else if (item.optional)
then "${key}? ${mkValue val}\n"
else "${key} ${mkValue val}\n";
mkConf = cfg: concatStrings (mapAttrsToList mkConfigLine cfg);
in mkConf exprs;
in
{
options = {
intermediateNixConfig = mkOption {
readOnly = true;
type = types.lines;
example = ''
USB? y
DEBUG n
'';
description = ''
The result of converting the structured kernel configuration in settings
to an intermediate string that can be parsed by generate-config.pl to
answer the kernel `make defconfig`.
'';
};
settings = mkOption {
type = types.attrsOf kernelItem;
example = literalExample '' with lib.kernel; {
"9P_NET" = yes;
USB = optional yes;
MMC_BLOCK_MINORS = freeform "32";
}'';
description = ''
Structured kernel configuration.
'';
};
};
config = {
intermediateNixConfig = generateNixKConf config.settings;
};
}