From 2d56559f04d43095467c4a37c46ad5a97e471f18 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Sat, 3 Oct 2026 06:36:33 -0500
Subject: [PATCH] [lvgl] Reject ESP8266 at validation (#20099)

---
 esphome/components/lvgl/__init__.py          |  9 +++++++++
 esphome/components/lvgl/lvgl_esphome.cpp     |  4 ++--
 tests/component_tests/lvgl/test_platforms.py | 14 ++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 tests/component_tests/lvgl/test_platforms.py

diff --git a/esphome/components/lvgl/__init__.py b/esphome/components/lvgl/__init__.py
index ca9a317fec..66aaac5301 100644
--- a/esphome/components/lvgl/__init__.py
+++ b/esphome/components/lvgl/__init__.py
@@ -48,6 +48,7 @@ from esphome.cpp_generator import MockObj
 from esphome.final_validate import full_config
 from esphome.helpers import write_file_if_changed
 from esphome.schema_extractors import SCHEMA_EXTRACT, schema_extractor
+from esphome.types import ConfigType
 from esphome.writer import clean_build
 from esphome.yaml_util import load_yaml
 
@@ -641,7 +642,15 @@ LVGL_TOP_LEVEL_SCHEMA = (
 )
 
 
+def _not_on_esp8266(config: ConfigType) -> ConfigType:
+    # ESP8266 does not have enough RAM for LVGL to be practical.
+    if CORE.is_esp8266:
+        raise cv.Invalid("LVGL is not supported on ESP8266")
+    return config
+
+
 LVGL_SCHEMA = cv.All(
+    _not_on_esp8266,
     container_schema(obj_spec, LVGL_TOP_LEVEL_SCHEMA),
     cv.has_at_most_one_key(CONF_PAGES, df.CONF_LAYOUT),
     add_hello_world,
diff --git a/esphome/components/lvgl/lvgl_esphome.cpp b/esphome/components/lvgl/lvgl_esphome.cpp
index 90a770ac3b..466d400023 100644
--- a/esphome/components/lvgl/lvgl_esphome.cpp
+++ b/esphome/components/lvgl/lvgl_esphome.cpp
@@ -1037,7 +1037,7 @@ void lv_mem_init() {}
 
 void lv_mem_deinit() {}
 
-#if defined(USE_HOST) || defined(USE_RP2) || defined(USE_ESP8266)
+#ifndef USE_ESP32
 void *lv_malloc_core(size_t size) {
   auto *ptr = malloc(size);  // NOLINT
   if (ptr == nullptr) {
@@ -1053,7 +1053,7 @@ static void *lv_alloc_draw_buf(size_t size, bool internal) {
   return malloc(size);  // NOLINT
 }
 
-#elif defined(USE_ESP32)
+#else
 static unsigned cap_bits = MALLOC_CAP_SPIRAM | MALLOC_CAP_8BIT;  // NOLINT
 
 static void *lv_alloc_draw_buf(size_t size, bool internal) {
diff --git a/tests/component_tests/lvgl/test_platforms.py b/tests/component_tests/lvgl/test_platforms.py
new file mode 100644
index 0000000000..ac4da769ee
--- /dev/null
+++ b/tests/component_tests/lvgl/test_platforms.py
@@ -0,0 +1,14 @@
+"""LVGL rejects ESP8266 at validation time."""
+
+import pytest
+
+from esphome.components import lvgl
+from esphome.config_validation import Invalid
+from esphome.const import PlatformFramework
+from tests.component_tests.types import SetCoreConfigCallable
+
+
+def test_esp8266_is_rejected(set_core_config: SetCoreConfigCallable) -> None:
+    set_core_config(PlatformFramework.ESP8266_ARDUINO)
+    with pytest.raises(Invalid, match="not supported on ESP8266"):
+        lvgl.CONFIG_SCHEMA({})