build: replace wasm patch with third_party/qemu submodule

The 7.7k-line qemu-wasm patch was really a fork, so vendor it as a submodule
(pinned at the xteink QEMU fork) and build it directly. Removes the
clone/commit-check/patch/reset machinery, the redundant web-dev/patch targets,
and 0002-qemu-wasm.patch. Editing third_party/qemu now recompiles incrementally
via plain `make web`. Native build keeps 0001-xteink-machine.patch.

.gitmodules

@@ -0,0 +1,4 @@
+[submodule "third_party/qemu"]
+	path = third_party/qemu
+	url = git@ssh.gitea.va.reichard.io:evan/qemu-xteink.git
+	branch = main

Makefile

@@ -5,15 +5,13 @@ FIRMWARE_DIR ?= $(FIRMWARE_REPO)/.pio/build/default
 SD_SRC ?= $(FIRMWARE_REPO)/sdcard
 QEMU_SRC ?= _scratch/qemu-src
 QEMU_BIN = $(QEMU_SRC)/build/qemu-system-riscv32
-QEMU_WASM_SRC ?= _scratch/qemu-wasm-src
+# QEMU source for the wasm build is the third_party/qemu submodule. Edit it in
-# Working tree for the fast dev loop: edit here, `make web-dev` compiles it incrementally.
+# place; `make web` recompiles only what changed, no patch round-trip.
-DEV_SRC ?= _scratch/qemu-fix-src
+QEMU_WASM_SRC ?= third_party/qemu
-# Commit the 0002 patch is diffed against when running `make patch`.
-PATCH_BASE ?= 610f8c69bc91dcb4ba81de1b7d2e74cc2adfb31e
 WASM_OUT ?= dist/wasm
 VARIANT ?= x3
 
-.PHONY: firmware sdimage qemu qemu-wasm qemu-wasm-dev web web-dev web-test patch run run-upstream chip clean
+.PHONY: firmware sdimage qemu qemu-wasm web web-test run run-upstream chip clean
 
 firmware:
 	esptool --chip esp32c3 merge-bin -o flash.bin \
@@ -33,23 +31,11 @@ qemu:
 qemu-wasm:
 	QEMU_WASM_SRC=$(QEMU_WASM_SRC) WASM_OUT=$(WASM_OUT) scripts/build-qemu-wasm.sh
 
-# Incremental build straight from $(DEV_SRC); no patch reset, so edits compile fast.
-qemu-wasm-dev:
-	QEMU_WASM_DEV=1 QEMU_WASM_SRC=$(DEV_SRC) WASM_OUT=$(WASM_OUT) scripts/build-qemu-wasm.sh
-
-# Regenerate the wasm patch from $(DEV_SRC) once the dev tree is where you want it.
-patch:
-	cd $(DEV_SRC) && git diff --binary $(PATCH_BASE) > $(CURDIR)/qemu/patches/0002-qemu-wasm.patch
-
 # Serve over HTTPS by default so headless/LAN access is cross-origin isolated. Override with WEB_TLS=.
 WEB_TLS ?= --tls
 web: qemu-wasm
 	python3 scripts/serve-web.py $(WEB_TLS)
 
-# Fast iteration: incremental compile from $(DEV_SRC), then serve. Run `make patch` before committing.
-web-dev: qemu-wasm-dev
-	python3 scripts/serve-web.py $(WEB_TLS)
-
 web-test:
 	node scripts/test-web.mjs
 

README.md

@@ -29,9 +29,15 @@ Point at a firmware build with `make firmware FIRMWARE_DIR=/path/to/.pio/build/g
 
 ## WebAssembly build
 
-Podman or Docker is required. The build is limited to `riscv32-softmmu` and the
+Podman or Docker is required. The QEMU source is the `third_party/qemu`
-X3/X4 device graph; networking, audio, virtfs, tools, docs, and unrelated boards
+submodule, so initialize it first:
-are disabled.
+
+```sh
+git submodule update --init third_party/qemu
+```
+
+The build is limited to `riscv32-softmmu` and the X3/X4 device graph;
+networking, audio, virtfs, tools, docs, and unrelated boards are disabled.
 
 ```sh
 make qemu-wasm
@@ -67,9 +73,11 @@ browser JS heap where supported. X4 remains a white display stub.
   and its device models (I²C fingerprints, ADC, GPIO, SPI2, X3 UC8253, X4 panel
   stub, SD-over-SPI fix), applied onto the pinned espressif/qemu commit by
   `scripts/build-qemu.sh`.
-- `qemu/patches/0002-qemu-wasm.patch` and `qemu/wasm/Dockerfile` — the pinned
+- `third_party/qemu` — submodule of the [xteink QEMU fork](git@ssh.gitea.va.reichard.io:evan/qemu-xteink.git)
-  qemu-wasm host backend port and minimal Emscripten dependency environment,
+  (espressif/qemu + the machine models + the wasm32 TCG backend), built for the
-  built by `scripts/build-qemu-wasm.sh`.
+  browser by `scripts/build-qemu-wasm.sh`. Edit it in place; `make web`
+  recompiles incrementally. `qemu/wasm/Dockerfile` is the pinned Emscripten
+  dependency environment.
 - `flake.nix` — the espressif-qemu *release* binary as the fast generic baseline
   (`nix run .#run-upstream -- flash.bin`), plus a devShell with QEMU's full build
   environment. `Makefile` — `qemu`, `firmware`, `sdimage`, `run`, `chip`.

scripts/build-qemu-wasm.sh

@@ -2,13 +2,12 @@
 set -euo pipefail
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd)"
-SRC="${QEMU_WASM_SRC:-$ROOT/_scratch/qemu-wasm-src}"
+# QEMU source is the third_party/qemu submodule (fork with the xteink machine +
+# wasm32 backend). Edit it in place; builds compile incrementally, no patching.
+SRC="${QEMU_WASM_SRC:-$ROOT/third_party/qemu}"
 OUT="${WASM_OUT:-$ROOT/dist/wasm}"
 [[ "$SRC" = /* ]] || SRC="$ROOT/$SRC"
 [[ "$OUT" = /* ]] || OUT="$ROOT/$OUT"
-TAG="esp-develop-9.2.2-20260417"
-COMMIT="40edccac415693c5130f91c01d84176ae6008566"
-QEMU_WASM_COMMIT="0ef7b4e2814b231705d8371dd7997f5b72e70baf"
 IMAGE="xteink-qemu-wasm-build"
 JOBS="${JOBS:-$(nproc 2>/dev/null || echo 2)}"
 
@@ -20,35 +19,13 @@ else
     ENGINE=docker
 fi
 
-# Dev Mode - Build directly out of an already-patched working tree (e.g. _scratch/qemu-fix-src);
+if [ ! -f "$SRC/tcg/wasm32.c" ]; then
-# skip clone/commit-check/patch so edits compile incrementally without the patch round-trip.
+    echo "third_party/qemu submodule not checked out; run: git submodule update --init" >&2
-if [ -n "${QEMU_WASM_DEV:-}" ]; then
+    exit 1
-    cd "$SRC"
-else
-    if [ ! -d "$SRC/.git" ]; then
-        git clone --depth 1 --branch "$TAG" https://github.com/espressif/qemu "$SRC"
-    fi
-
-    cd "$SRC"
-    if [ "$(git rev-parse HEAD)" != "$COMMIT" ]; then
-        echo "QEMU source must be $COMMIT ($TAG)" >&2
-        exit 1
-    fi
-
-    # Re-apply Patches On Drift - The source tree is a build artifact of the patches; reset and re-apply whenever a patch is newer than the last apply so `make web` never silently rebuilds stale sources.
-    STAMP=".xteink-patch-stamp"
-    if [ ! -f hw/display/xteink_x3_eink.c ] || [ ! -f tcg/wasm32.c ] \
-        || [ "$ROOT/qemu/patches/0001-xteink-machine.patch" -nt "$STAMP" ] \
-        || [ "$ROOT/qemu/patches/0002-qemu-wasm.patch" -nt "$STAMP" ]; then
-        git reset --hard "$COMMIT"
-        git clean -fdx -e build
-        git apply "$ROOT/qemu/patches/0001-xteink-machine.patch"
-        git apply --whitespace=nowarn "$ROOT/qemu/patches/0002-qemu-wasm.patch"
-        touch "$STAMP"
-    fi
 fi
+cd "$SRC"
 
-printf 'Building Emscripten environment (qemu-wasm %s)\n' "$QEMU_WASM_COMMIT"
+printf 'Building Emscripten environment for %s\n' "$SRC"
 "$ENGINE" build -t "$IMAGE" -f "$ROOT/qemu/wasm/Dockerfile" "$ROOT/qemu/wasm"
 
 FLAGS="-O3 -Wno-error=unused-command-line-argument -matomics -mbulk-memory -DNDEBUG -DG_DISABLE_ASSERT -D_GNU_SOURCE -sASYNCIFY=1 -pthread -sPROXY_TO_PTHREAD=1 -sFORCE_FILESYSTEM -sALLOW_TABLE_GROWTH -sINITIAL_MEMORY=64MB -sALLOW_MEMORY_GROWTH=1 -sMAXIMUM_MEMORY=1GB -sSTACK_SIZE=1048576 -sWASM_BIGINT -sMALLOC=mimalloc -sEXPORT_ES6=1 -sASYNCIFY_IMPORTS=ffi_call_js"