tftp: introduce an alternative command line for TFTP

Normal command line and TFTP command line can be sometimes very
different.

e.g. We don't want to load UBI filesystems for a TFTP boot as it may
interfere with our root device loading.

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

modules/arch/mips.nix

@@ -14,5 +14,8 @@
     boot.commandLine = [
       "console=ttyS0,115200" # true of all mips we've yet encountered
     ];
+    boot.tftp.commandLine = [
+      "console=ttyS0,115200" # true of all mips we've yet encountered
+    ];
   };
 }

modules/base.nix

@@ -111,6 +111,12 @@ in {
     ++ lib.optional (config.rootOptions != null) "rootflags=${config.rootOptions}"
     ++ lib.optional (config.hardware.alternativeRootDevice != null) "altroot=${config.hardware.alternativeRootDevice}";
 
+    boot.tftp.commandLine = [
+      "panic=10 oops=panic init=/bin/init loglevel=8"
+      "fw_devlink=off"
+      "rootfstype=${config.rootfsType}"
+    ];
+
     system.callService = path : parameters :
       let
         typeChecked = caller: type: value:

modules/outputs/tftpboot.nix

@@ -28,6 +28,14 @@ in {
       type = types.bool;
       default = false;
     };
+    commandLine = mkOption {
+      type = types.listOf types.str;
+      default = config.boot.commandLine;
+      description = ''
+        TFTP-specific command line.
+        Defaults to the classical one if unset.
+      '';
+    };
   };
   options.system.outputs = {
     tftpboot = mkOption {
@@ -105,7 +113,7 @@ in {
             zimage = "bootz";
           }; in choices.${cfg.kernelFormat};
 
-          cmdline = concatStringsSep " " config.boot.commandLine;
+          cmdline = concatStringsSep " " config.boot.tftp.commandLine;
           objcopy = "${pkgs.stdenv.cc.bintools.targetPrefix}objcopy";
           stripAndZip = ''
             ${objcopy} -O binary -R .reginfo -R .notes -R .note -R .comment -R .mdebug -R .note.gnu.build-id -S vmlinux.elf vmlinux.bin

modules/outputs/ubivolume.nix

@@ -29,6 +29,13 @@ in
       };
       boot.initramfs.enable = true;
 
+      # In TFTP, the device named "rootfs" is the UBI device.
+      # We tell the kernel to load it.
+      # This avoids interference from the other UBI volumes.
+      boot.tftp.commandLine = [
+        "ubi.mtd=rootfs"
+      ];
+
       system.outputs.rootfs =
       let
         inherit (pkgs.pkgsBuildBuild) runCommand;