From 2086e35e6657ae29b77e0839f0251fbb79f03f5c Mon Sep 17 00:00:00 2001
From: tgasslander <tobias@gasslander.com>
Date: Sun, 4 Jan 2026 16:29:12 +0100
Subject: [PATCH 1/2] add build instructions

---
 README.md | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/README.md b/README.md
index 91196451..1c14532f 100644
--- a/README.md
+++ b/README.md
@@ -3,9 +3,11 @@ Lightweight Docker images for [ZMK][zmk].
 ### Platforms
 
 #### Tested
+
 - `arm`
 
 #### Not Tested
+
 - `arc`
 - `arm64`
 - `mips`
@@ -23,6 +25,24 @@ Lightweight Docker images for [ZMK][zmk].
 
 ### Images
 
+#### Build arguments
+
+The building of the image requires the following build arguments:
+
+- `ZEPHYR_VERSION`: version of [Zephyr][zephyr] to install (e.g. `4.1.0`)
+- `ARCHITECTURE`: target architecture (e.g. `arm`, `x86_64`, etc.)
+- `ZEPHYR_SDK_VERSION`: version of [Zephyr SDK][Zephyr SDK] to install (e.g. `0.17.4`)
+
+Example:
+
+```shell
+docker build \
+    --build-arg ZEPHYR_VERSION=4.1.0 \
+    --build-arg ARCHITECTURE=x86_64 \
+    --build-arg ZEPHYR_SDK_VERSION=0.17.4 \
+    -t zmkfirmware/zmk-docker .
+```
+
 #### build
 
 For _building_ [ZMK][zmk] firmware with CI.
@@ -47,3 +67,4 @@ For _developing_ [ZMK][zmk] (firmware and documentation).
 [ubuntu]: https://hub.docker.com/_/ubuntu "Ubuntu"
 [zephyr]: https://github.com/zephyrproject-rtos/zephyr "Zephyr"
 [zmk]: https://github.com/zmkfirmware/zmk "ZMK"
+[zephyr sdk]: https://github.com/zephyrproject-rtos/sdk-ng/tags "Zephyr SDK"

From 21cacf3be837fb8856fd3c62c7f50ddb9bcef721 Mon Sep 17 00:00:00 2001
From: tgasslander <tobias@gasslander.com>
Date: Sun, 4 Jan 2026 16:29:32 +0100
Subject: [PATCH 2/2] move ARG ZEPHYR_SDK_INSTALL_DIR assignment

ARGs don't survive between stages.
Moved it to where it's being used.
---
 Dockerfile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Dockerfile b/Dockerfile
index e2523cd9..567468ce 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -90,7 +90,6 @@ FROM common AS build
 
 ARG ARCHITECTURE
 ARG ZEPHYR_SDK_VERSION
-ARG ZEPHYR_SDK_INSTALL_DIR=/opt/zephyr-sdk-${ZEPHYR_SDK_VERSION}
 RUN \
   export minimal_sdk_file_name="zephyr-sdk-${ZEPHYR_SDK_VERSION}_linux-$(uname -m)_minimal" \
   && if [ "${ARCHITECTURE}" = "arm" ]; then arch_format="eabi"; else arch_format="elf"; fi \
@@ -116,5 +115,7 @@ RUN \
 #------------------------------------------------------------------------------
 
 FROM dev-generic AS dev
+ARG ZEPHYR_SDK_INSTALL_DIR=/opt/zephyr-sdk-${ZEPHYR_SDK_VERSION}
 
 COPY --from=build ${ZEPHYR_SDK_INSTALL_DIR} ${ZEPHYR_SDK_INSTALL_DIR}
+