bcachefs-kernel-module: Nest within bcachefs-tools (#446975)

nixos/modules/tasks/filesystems/bcachefs.nix

@@ -178,8 +178,20 @@ let
 in
 
 {
-  options.boot.bcachefs.package = lib.mkPackageOption pkgs "bcachefs-tools" { } // {
-    description = "Configured Bcachefs userspace package.";
+  options.boot.bcachefs = {
+    package = lib.mkPackageOption pkgs "bcachefs-tools" {
+      extraDescription = ''
+        This package should also provide a passthru 'kernelModule'
+        attribute to build the out-of-tree kernel module.
+      '';
+    };
+
+    modulePackage = lib.mkOption {
+      type = lib.types.package;
+      # See NOTE in linux-kernels.nix
+      default = config.boot.kernelPackages.callPackage cfg.package.kernelModule { };
+      internal = true;
+    };
   };
 
   options.services.bcachefs.autoScrub = {
@@ -245,8 +257,8 @@ in
         system.fsPackages = [ cfg.package ];
         services.udev.packages = [ cfg.package ];
 
-        boot.extraModulePackages = lib.optionals (!config.boot.kernelPackages.bcachefs.meta.broken) [
-          config.boot.kernelPackages.bcachefs
+        boot.extraModulePackages = lib.optionals (!cfg.modulePackage.meta.broken) [
+          cfg.modulePackage
         ];
 
         systemd = {

pkgs/by-name/bc/bcachefs-tools/kernel-module.nix

@@ -1,7 +1,7 @@
+bcachefs-tools:
 {
   lib,
   stdenv,
-  bcachefs-tools,
   kernelModuleMakeFlags,
   kernel,
 }:

pkgs/by-name/bc/bcachefs-tools/package.nix

@@ -118,6 +118,9 @@ stdenv.mkDerivation (finalAttrs: {
   '';
 
   passthru = {
+    # See NOTE in linux-kernels.nix
+    kernelModule = import ./kernel-module.nix finalAttrs.finalPackage;
+
     tests = {
       version = testers.testVersion {
         package = finalAttrs.finalPackage;

pkgs/top-level/linux-kernels.nix

@@ -375,7 +375,11 @@ in
 
         bbswitch = callPackage ../os-specific/linux/bbswitch { };
 
-        bcachefs = callPackage ../os-specific/linux/bcachefs-kernel-module { };
+        # NOTE: The bcachefs module is called this way to facilitate
+        # easy overriding, as it is expected many users will want to
+        # pull from the upstream git repo, which may include
+        # unreleased changes to the module build process.
+        bcachefs = callPackage pkgs.bcachefs-tools.kernelModule { };
 
         ch9344 = callPackage ../os-specific/linux/ch9344 { };