Support building EC firmware for Novacustom

[tlaurion]

To build EC, some changes are needed for Heads to build it and add it in rom from a Heads future commit so it's automatically flashed as part as internal upgrade alongside coreboot. Users should not care.

The nix docker image will need to be updated with required deps and first build successfully.

Following https://docs.dasharo.com/unified/novacustom/recovery/#ec-firmware-recovery

Debian deps equiv to nix will be needed:

• avr-libc avrdude binutils-avr clang-format clang-format-19 gcc-avr libcap-dev libftdi1 libhidapi-dev libhidapi-libusb0 libudev-dev libusb-0.1-4 sdcc sdcc-libraries
  (map to nix equivalents and put under flake.nix with high level deps which should install lower ones)

• As well as cargo and probably others

---

Error on debian-13 following upstream docs :

user@debian-13:~/ec$ make BOARD=arduino/mega2560
  CC        arduino/mega2560/2026-01-12_6d9d6cf/arch/avr/gpio.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/arch/avr/i2c.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/arch/avr/i2c_slave.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/arch/avr/uart.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/board/arduino/mega2560/battery.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/board/arduino/mega2560/i2c.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/board/arduino/mega2560/main.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/board/arduino/mega2560/parallel.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/common/i2c.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/common/keymap.o
  CC        arduino/mega2560/2026-01-12_6d9d6cf/common/version.o
  LINK      arduino/mega2560/2026-01-12_6d9d6cf/ec.elf
  OBJCOPY   arduino/mega2560/2026-01-12_6d9d6cf/ec.ihx
  OBJCOPY   arduino/mega2560/2026-01-12_6d9d6cf/ec.rom
avr-objcopy: build/arduino/mega2560/2026-01-12_6d9d6cf/ec.ihx: invalid operation
make: *** [src/arch/avr/toolchain.mk:24: build/arduino/mega2560/2026-01-12_6d9d6cf/ec.rom] Error 1

Attached make -d output cc @mkopec (note that debian is not supposed to be supported, just info:
make_debug_on_debian_13.txt

---

Input for #2039

TODO:

• add tooling in Heads so "System Information" can provide current EC version
• nix flake.nix maybe flake.lock will adapted with all EC builder needed dependencies
• add target/mega2560.mk to build EC
• boards configs adding target/mega2560.mk
• coreboot configs point to ec.rom for coreboot configs to have

CONFIG_EC_SYSTEM76_EC_UPDATE=y
CONFIG_EC_SYSTEM76_EC_UPDATE_FILE="ec.rom"

or DASHARO_EC counterpart?

Something else @mkopec ?

[tlaurion]

Hmmm... avr-gcc not directly available

As of current attempts to bring EC buildstack avail:

user@debian-13:~/heads$ git diff origin/master flake.nix 
diff --git a/flake.nix b/flake.nix
index 0b985424a0..33b36f8c90 100644
--- a/flake.nix
+++ b/flake.nix
@@ -22,12 +22,14 @@
       deps = with pkgs; [
         # Core build utilities
         autoconf
+        avrdude  # Dasharo EC build
         automake
         bashInteractive
         coreutils #basic tools like ls, cp, mv, kill)
         bc
         bison # Generate flashmap descriptor parser
         bzip2
+        cargo # Dasharo EC build
         cacert
         ccache
         coreboot-utils #consumed by diffoscope for ifdtool cbfsutils etc
@@ -63,6 +65,7 @@
         psmisc #process tools like killall, pstree, etc
         python3 # me_cleaner, coreboot
         rsync # coreboot
+        sdcc  # Dasharo EC build
         sharutils
         texinfo
         unzip

Not enough. We might need custom flake support :/

Reminder that ./docker_local_dev.sh is there to help iterate on that; buildsystem will rebuild nix base+ docker image if either flake.nix/flake.lock is uncommited, and reuse recent locally assembled docker image (per uncommitted changes)

[tlaurion]

user@debian-13:~/heads$ git diff ./docker_local_dev.sh
user@debian-13:~/heads$ git diff flake.nix
diff --git a/flake.nix b/flake.nix
index 80a1c79d3d..fb2d09ca22 100644
--- a/flake.nix
+++ b/flake.nix
@@ -22,6 +22,7 @@
       deps = with pkgs; [
         # Core build utilities
         autoconf
+        avrdude  # Dasharo EC build
         automake
         bashInteractive
         coreutils #basic tools like ls, cp, mv, kill)
@@ -60,10 +61,13 @@
         patch
         perl
         pkg-config
+        pkgsCross.avr.buildPackages.gcc # Dasharo EC build
+        pkgsCross.avr.libcCross # Dasharo EC build
         procps #process tools like free, pidof, pkill, top, vmstat, watch, etc
         psmisc #process tools like killall, pstree, etc
         python3 # me_cleaner, coreboot
         rsync # coreboot
+        sdcc  # Dasharo EC build
         sharutils
         texinfo
         unzip

Then needed:

./docker_local_dev.sh
[...]
cd build/x86/
git clone https://github.com/Dasharo/ec.git
cd ec
git submodule update --init --checkout
export NIX_CFLAGS_COMPILE_FOR_TARGET="-Wno-error=array-bounds"
make BOARD=arduino/mega2560
[...]
/nix/store/ri3vh5m2v0psmj446lqkafbyz6qbbiwm-avr-binutils-2.41/bin/avr-ld: skipping incompatible /nix/store/bhh2qwvgxhm0nh7d8plii3kd7l7q82gs-avr-libc-avr-2.1.0/avr/lib/avr5/libm.a when searching for -lm
/nix/store/ri3vh5m2v0psmj446lqkafbyz6qbbiwm-avr-binutils-2.41/bin/avr-ld: skipping incompatible /nix/store/bhh2qwvgxhm0nh7d8plii3kd7l7q82gs-avr-libc-avr-2.1.0/avr/lib/avr3/libm.a when searching for -lm
/nix/store/ri3vh5m2v0psmj446lqkafbyz6qbbiwm-avr-binutils-2.41/bin/avr-ld: skipping incompatible /nix/store/bhh2qwvgxhm0nh7d8plii3kd7l7q82gs-avr-libc-avr-2.1.0/avr/lib/avr4/libm.a when searching for -lm
/nix/store/ri3vh5m2v0psmj446lqkafbyz6qbbiwm-avr-binutils-2.41/bin/avr-ld: skipping incompatible /nix/store/bhh2qwvgxhm0nh7d8plii3kd7l7q82gs-avr-libc-avr-2.1.0/avr/lib/avr5/libc.a when searching for -lc
/nix/store/ri3vh5m2v0psmj446lqkafbyz6qbbiwm-avr-binutils-2.41/bin/avr-ld: skipping incompatible /nix/store/bhh2qwvgxhm0nh7d8plii3kd7l7q82gs-avr-libc-avr-2.1.0/avr/lib/avr3/libc.a when searching for -lc
/nix/store/ri3vh5m2v0psmj446lqkafbyz6qbbiwm-avr-binutils-2.41/bin/avr-ld: skipping incompatible /nix/store/bhh2qwvgxhm0nh7d8plii3kd7l7q82gs-avr-libc-avr-2.1.0/avr/lib/avr4/libc.a when searching for -lc
  OBJCOPY   arduino/mega2560/2026-01-12_6d9d6cf/ec.ihx
  OBJCOPY   arduino/mega2560/2026-01-12_6d9d6cf/ec.rom
Built 2026-01-12_6d9d6cf for arduino/mega2560

[tlaurion]

@mkopec we continue in that path? Guidance/PR welcome :)

[tlaurion]

@mkopec tlaurion@3b2aeea provides reproducible docker image providing requirements to build Dasharo EC.

Next step is either to provide a modules/dasharo-ec or a target/dasharo-ec, modify coreboot configs to activate dasahro ec + update and test? Can you iterate on that?

I added the present work to #2039 which sould build that PR successfully. Feel free to add commit to that PR and or fork my branch there? Otherwise what plan do you propose?