extract phram.mtd ramdisk support from tftpboot module

also rename tftproot output to tftpboot for consistency

devices/gl-ar750/default.nix

@@ -87,7 +87,7 @@
       inherit (pkgs.liminix.networking) interface;
     in {
       hardware = {
-        defaultOutput = "tftproot";
+        defaultOutput = "tftpboot";
         loadAddress = "0x80060000";
         entryPoint  = "0x80060000";
         flash = {

devices/gl-mt300a/default.nix

@@ -34,7 +34,7 @@
       };
      in {
       hardware = {
-        defaultOutput = "tftproot";
+        defaultOutput = "tftpboot";
         loadAddress = "0x80000000";
         entryPoint  = "0x80000000";
 

devices/gl-mt300n-v2/default.nix

@@ -41,7 +41,7 @@
         };
       };
       hardware = {
-        defaultOutput = "tftproot";
+        defaultOutput = "tftpboot";
         loadAddress = "0x80000000";
         entryPoint  = "0x80000000";
 

doc/developer.rst

@@ -121,7 +121,7 @@ image instead of flashing. In your device configuration add
     ipaddr = "192.168.200.251";
   };
 
-and then build ``outputs.tftproot``. This creates a file in
+and then build ``outputs.tftpboot``. This creates a file in
 ``result/`` called ``boot.scr``, which you can copy and paste into
 U-Boot to transfer the kernel and filesystem over TFTP and boot the
 kernel from RAM.

modules/ramdisk.nix

@@ -0,0 +1,34 @@
+{
+  config
+, pkgs
+, lib
+, ...
+}:
+let
+  inherit (lib) mkIf mkEnableOption mkOption; # types concatStringsSep;
+in {
+  options = {
+    boot = {
+      ramdisk = {
+        enable = mkEnableOption (lib.mdDoc ''
+          Configure kernel to enable reserving part of memory as
+          an MTD-based RAM disk.  Needed for TFTP booting or for
+          kexec-based revertable upgrade
+        '');
+      };
+    };
+  };
+  config = mkIf config.boot.ramdisk.enable {
+    kernel = {
+      config = {
+        MTD = "y";
+        MTD_PHRAM = "y";
+        MTD_CMDLINE_PARTS = "y";
+        MTD_OF_PARTS = "y";
+        PARTITION_ADVANCED = "y";
+        MTD_BLKDEVS = "y";
+        MTD_BLOCK = "y";
+      };
+    };
+  };
+}

modules/tftpboot.nix

@@ -20,32 +20,14 @@ in {
       };
     };
   };
+  imports = [ ./ramdisk.nix ];
   config = {
-    kernel = {
+    boot.ramdisk.enable = true;
-      config = {
+    kernel.config.MIPS_CMDLINE_FROM_BOOTLOADER = "y";
-        MTD = "y";
-        MTD_PHRAM = "y";
-        MTD_CMDLINE_PARTS = "y";
-        MIPS_CMDLINE_FROM_BOOTLOADER = "y";
 
-        # one or more of the following is required to get from
+    outputs.tftpboot =
-        # VFS: Cannot open root device "1f00" or unknown-block(31,0): error -6
-        # to
-        # VFS: Mounted root (squashfs filesystem) readonly on device 31:0.
-        MTD_OF_PARTS = "y";
-        PARTITION_ADVANCED = "y";
-        MSDOS_PARTITION = "y";
-        EFI_PARTITION = "y";
-        MTD_BLKDEVS = "y";
-        MTD_BLOCK = "y";
-
-        # CONFIG_MTD_MTDRAM=m         c'est quoi?
-      };
-
-    };
-    outputs.tftproot =
       let o = config.outputs; in
-      pkgs.runCommand "tftproot" {} ''
+      pkgs.runCommand "tftpboot" {} ''
         mkdir $out
         cd $out
         ln -s ${o.squashfs} squashfs
@@ -60,12 +42,13 @@ in {
       let
         inherit (pkgs.lib.trivial) toHexString;
       in
-        pkgs.buildPackages.runCommand "" {} ''
+        pkgs.buildPackages.runCommand "boot-scr" {} ''
           uimageSize=$(($(stat -L -c %s ${config.outputs.uimage}) + 0x1000 &(~0xfff)))
           squashfsStart=0x$(printf %x $((${cfg.loadAddress} + 0x100000 + $uimageSize)))
           squashfsBytes=$(($(stat -L -c %s ${config.outputs.squashfs}) + 0x100000 &(~0xfffff)))
           squashfsMb=$(($squashfsBytes >> 20))
           cmd="mtdparts=phram0:''${squashfsMb}M(nix) phram.phram=phram0,''${squashfsStart},''${squashfsMb}Mi memmap=''${squashfsMb}M\$''${squashfsStart} root=1f00";
+
           cat > $out << EOF
           setenv serverip ${cfg.serverip}
           setenv ipaddr ${cfg.ipaddr}
@@ -74,6 +57,5 @@ in {
           bootm 0x$(printf %x ${cfg.loadAddress})
           EOF
         '';
-
   };
 }