From 4fbec87a5bfc11e60b98523e55c813c6fadf655b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Forsman?= <bjorn.forsman@gmail.com>
Date: Sat, 5 Nov 2022 10:16:58 +0100
Subject: [PATCH] nixos/sane: point env vars to /etc for quick reload

Point $SANE_CONFIG_DIR and $LD_LIBRARY_PATH to symlinks in /etc, instead
of directly to nix store paths, so that activating a new configuration
takes effect immediately, instead of requiring users to re-login.
---
 nixos/modules/services/hardware/sane.nix | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/nixos/modules/services/hardware/sane.nix b/nixos/modules/services/hardware/sane.nix
index 5455cf56e8a..1d4489877b2 100644
--- a/nixos/modules/services/hardware/sane.nix
+++ b/nixos/modules/services/hardware/sane.nix
@@ -28,8 +28,8 @@ let
   };
 
   env = {
-    SANE_CONFIG_DIR = config.hardware.sane.configDir;
-    LD_LIBRARY_PATH = [ "${saneConfig}/lib/sane" ];
+    SANE_CONFIG_DIR = "/etc/sane.d";
+    LD_LIBRARY_PATH = [ "/etc/sane-libs" ];
   };
 
   backends = [ pkg netConf ] ++ optional config.services.saned.enable sanedConf ++ config.hardware.sane.extraBackends;
@@ -156,6 +156,8 @@ in
 
       environment.systemPackages = backends;
       environment.sessionVariables = env;
+      environment.etc."sane.d".source = config.hardware.sane.configDir;
+      environment.etc."sane-libs".source = "${saneConfig}/lib/sane";
       services.udev.packages = backends;
 
       users.groups.scanner.gid = config.ids.gids.scanner;