[display] Loop on the reader's step in display drivers and cap mipi_spi args in the reader

mipi_spi, mipi_dsi and mipi_rgb also switch to config_has_writer, and the
mipi_spi argument limit uses cv.Length instead of a wrapper function.

esphome/components/display/__init__.py

@@ -220,10 +220,7 @@ def get_display_metadata(display_id: ID) -> DisplayMetaData:
         height=dimensions[1],
         has_hardware_rotation=False,
         byte_order=disp_config.get(CONF_BYTE_ORDER, cv.UNDEFINED),
-        has_writer=disp_config.get(CONF_AUTO_CLEAR_ENABLED) is True
-        or disp_config.get(CONF_PAGES) is not None
-        or disp_config.get(CONF_LAMBDA) is not None
-        or disp_config.get(CONF_SHOW_TEST_CARD) is True,
+        has_writer=config_has_writer(disp_config),
         rotation=disp_config.get(CONF_ROTATION, 0),
         draw_rounding=disp_config.get(CONF_DRAW_ROUNDING, 0),
     )

esphome/components/epaper_spi/display.py

@@ -15,7 +15,6 @@ from esphome.components.mipi import (
 import esphome.config_validation as cv
 from esphome.config_validation import update_interval
 from esphome.const import (
-    CONF_AUTO_CLEAR_ENABLED,
     CONF_BUSY_PIN,
     CONF_CS_PIN,
     CONF_DATA_RATE,
@@ -189,10 +188,7 @@ def customise_schema(config):
         height,
         has_hardware_rotation=True,
         byte_order=cv.UNDEFINED,
-        has_writer=config.get(CONF_AUTO_CLEAR_ENABLED) is True
-        or config.get(CONF_PAGES) is not None
-        or config.get(CONF_LAMBDA) is not None
-        or config.get(CONF_SHOW_TEST_CARD) is True,
+        has_writer=display.config_has_writer(config),
         rotation=config.get(CONF_ROTATION, 0),
         draw_rounding=0,
     )

esphome/components/epaper_spi/epaper_spi.cpp

@@ -1,4 +1,5 @@
 #include "epaper_spi.h"
+#include "esphome/components/display/init_sequence.h"
 #include <cinttypes>
 #include "esphome/core/application.h"
 #include "esphome/core/helpers.h"
@@ -315,26 +316,18 @@ void EPaperBase::start_data_() {
 void EPaperBase::on_safe_shutdown() { this->deep_sleep(); }
 
 void EPaperBase::send_init_sequence_(const uint8_t *sequence, size_t length) {
-  size_t index = 0;
-
-  while (index != length) {
-    if (length - index < 2) {
+  display::InitSequenceReader reader(sequence, length);
+  display::InitSequenceEntry entry;
+  while (auto step = reader.next(entry)) {
+    if (step == display::INIT_SEQUENCE_STEP_MALFORMED) {
       this->mark_failed(LOG_STR("Malformed init sequence"));
       return;
     }
-    const uint8_t cmd = sequence[index++];
-    if (const uint8_t x = sequence[index++]; x == DELAY_FLAG) {
-      ESP_LOGV(TAG, "Delay %dms", cmd);
-      delay(cmd);
+    if (step == display::INIT_SEQUENCE_STEP_DELAY) {
+      ESP_LOGV(TAG, "Delay %dms", entry.value);
+      delay(entry.value);
     } else {
-      const uint8_t num_args = x & 0x7F;
-      if (length - index < num_args) {
-        ESP_LOGE(TAG, "Malformed init sequence, cmd = %X, num_args = %u", cmd, num_args);
-        this->mark_failed();
-        return;
-      }
-      this->cmd_data(cmd, sequence + index, num_args);
-      index += num_args;
+      this->cmd_data(entry.value, entry.args, entry.count);
     }
   }
 }

esphome/components/epaper_spi/epaper_spi.h

@@ -34,7 +34,6 @@ static constexpr uint32_t MAX_TRANSFER_TIME = 10;  // Transfer in 10ms blocks to
 static constexpr size_t MAX_TRANSFER_SIZE = 128;
 // Longer busy waits are the waveform or a stuck pin, and are polled at the normal loop pace
 static constexpr uint32_t FAST_BUSY_POLL_MS = 50;
-static constexpr uint8_t DELAY_FLAG = 0xFF;
 
 class EPaperBase : public Display,
                    public spi::SPIDevice<spi::BIT_ORDER_MSB_FIRST, spi::CLOCK_POLARITY_LOW, spi::CLOCK_PHASE_LEADING,

esphome/components/mipi_dsi/display.py

@@ -38,7 +38,6 @@ from esphome.components.mipi import (
 )
 import esphome.config_validation as cv
 from esphome.const import (
-    CONF_AUTO_CLEAR_ENABLED,
     CONF_COLOR_ORDER,
     CONF_DIMENSIONS,
     CONF_ENABLE_PIN,
@@ -167,8 +166,7 @@ def _config_schema(config: ConfigType) -> ConfigType:
         height,
         has_hardware_rotation=False,
         byte_order=config[CONF_BYTE_ORDER],
-        has_writer=requires_buffer(config)
-        or config.get(CONF_AUTO_CLEAR_ENABLED) is True,
+        has_writer=display.config_has_writer(config),
         rotation=config.get(CONF_ROTATION, 0),
         draw_rounding=config.get(CONF_DRAW_ROUNDING, 0),
     )

esphome/components/mipi_dsi/mipi_dsi.cpp

@@ -1,6 +1,7 @@
 #ifdef USE_ESP32_VARIANT_ESP32P4
 #include <utility>
 #include "mipi_dsi.h"
+#include "esphome/components/display/init_sequence.h"
 #include "esphome/core/helpers.h"
 
 #include <algorithm>
@@ -123,47 +124,38 @@ void MipiDsi::setup() {
     this->smark_failed(LOG_STR("esp_lcd_init failed"), err);
     return;
   }
-  size_t index = 0;
-  const uint8_t *seq = this->init_sequence_;
-  const size_t len = this->init_sequence_len_;
-  while (index != len) {
-    if (len - index < 2) {
+  display::InitSequenceReader reader(this->init_sequence_, this->init_sequence_len_);
+  display::InitSequenceEntry entry;
+  while (auto step = reader.next(entry)) {
+    if (step == display::INIT_SEQUENCE_STEP_MALFORMED) {
       this->mark_failed(LOG_STR("Malformed init sequence"));
       return;
     }
-    uint8_t cmd = seq[index++];
-    uint8_t x = seq[index++];
-    if (x == DELAY_FLAG) {
-      ESP_LOGD(TAG, "Delay %dms", cmd);
-      delay(cmd);
-    } else {
-      uint8_t num_args = x & 0x7F;
-      if (len - index < num_args) {
-        this->mark_failed(LOG_STR("Malformed init sequence"));
-        return;
-      }
-      if (cmd == SLEEP_OUT) {
-        // are we ready, boots?
-        int duration = when - millis();
-        if (duration > 0) {
-          delay(duration);
-        }
-      }
-      const auto *ptr = seq + index;
-#if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
-      char hex_buf[format_hex_pretty_size(MIPI_DSI_MAX_CMD_LOG_BYTES)];
-#endif
-      ESP_LOGVV(TAG, "Command %02X, length %d, byte(s) %s", cmd, num_args,
-                format_hex_pretty_to(hex_buf, ptr, num_args, '.'));
-      err = esp_lcd_panel_io_tx_param(this->io_handle_, cmd, ptr, num_args);
-      if (err != ESP_OK) {
-        this->smark_failed(LOG_STR("lcd_panel_io_tx_param failed"), err);
-        return;
-      }
-      index += num_args;
-      if (cmd == SLEEP_OUT)
-        delay(10);
+    if (step == display::INIT_SEQUENCE_STEP_DELAY) {
+      ESP_LOGD(TAG, "Delay %dms", entry.value);
+      delay(entry.value);
+      continue;
     }
+    const uint8_t cmd = entry.value;
+    if (cmd == SLEEP_OUT) {
+      // are we ready, boots?
+      int duration = when - millis();
+      if (duration > 0) {
+        delay(duration);
+      }
+    }
+#if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
+    char hex_buf[format_hex_pretty_size(MIPI_DSI_MAX_CMD_LOG_BYTES)];
+#endif
+    ESP_LOGVV(TAG, "Command %02X, length %d, byte(s) %s", cmd, entry.count,
+              format_hex_pretty_to(hex_buf, entry.args, entry.count, '.'));
+    err = esp_lcd_panel_io_tx_param(this->io_handle_, cmd, entry.args, entry.count);
+    if (err != ESP_OK) {
+      this->smark_failed(LOG_STR("lcd_panel_io_tx_param failed"), err);
+      return;
+    }
+    if (cmd == SLEEP_OUT)
+      delay(10);
   }
   this->io_lock_ = xSemaphoreCreateBinary();
   esp_lcd_dpi_panel_event_callbacks_t cbs = {

esphome/components/mipi_dsi/mipi_dsi.h

@@ -31,7 +31,6 @@ const uint8_t INVERT_OFF = 0x20;
 const uint8_t INVERT_ON = 0x21;
 const uint8_t DISPLAY_ON = 0x29;
 const uint8_t CMD2_BKSEL = 0xFF;
-const uint8_t DELAY_FLAG = 0xFF;
 const uint8_t MADCTL_BGR = 0x08;
 const uint8_t MADCTL_MX = 0x40;
 const uint8_t MADCTL_MY = 0x80;

esphome/components/mipi_rgb/display.py

@@ -50,7 +50,6 @@ from esphome.components.spi import (
 )
 import esphome.config_validation as cv
 from esphome.const import (
-    CONF_AUTO_CLEAR_ENABLED,
     CONF_BLUE,
     CONF_COLOR_ORDER,
     CONF_CS_PIN,
@@ -243,8 +242,7 @@ def _config_schema(config: ConfigType) -> ConfigType:
         height,
         has_hardware_rotation=True,
         byte_order=config[CONF_BYTE_ORDER],
-        has_writer=requires_buffer(config)
-        or config.get(CONF_AUTO_CLEAR_ENABLED) is True,
+        has_writer=display.config_has_writer(config),
         rotation=config.get(CONF_ROTATION, 0),
         draw_rounding=config.get(CONF_DRAW_ROUNDING, 0),
     )

esphome/components/mipi_rgb/mipi_rgb.cpp

@@ -1,5 +1,6 @@
 #if defined(USE_ESP32_VARIANT_ESP32S3) || defined(USE_ESP32_VARIANT_ESP32P4) || defined(USE_ESP32_VARIANT_ESP32S31)
 #include "mipi_rgb.h"
+#include "esphome/components/display/init_sequence.h"
 #include "esphome/core/gpio.h"
 #include "esphome/core/hal.h"
 #include "esphome/core/helpers.h"
@@ -13,8 +14,6 @@
 
 namespace esphome::mipi_rgb {
 
-static const uint8_t DELAY_FLAG = 0xFF;
-
 // Maximum bytes to log for init commands (truncated if larger)
 static constexpr size_t MIPI_RGB_MAX_CMD_LOG_BYTES = 64;
 static constexpr uint8_t MADCTL_MY = 0x80;     // Bit 7 Bottom to top
@@ -75,44 +74,30 @@ void MipiRgbSpi::write_data_(uint8_t value) {
   this->disable();
 }
 
-/**
- * this relies upon the init sequence being well-formed, which is guaranteed by the Python init code.
- */
-
 void MipiRgbSpi::write_init_sequence_() {
-  size_t index = 0;
-  const uint8_t *seq = this->init_sequence_;
-  const size_t len = this->init_sequence_len_;
-  while (index != len) {
-    if (len - index < 2) {
+  display::InitSequenceReader reader(this->init_sequence_, this->init_sequence_len_);
+  display::InitSequenceEntry entry;
+  while (auto step = reader.next(entry)) {
+    if (step == display::INIT_SEQUENCE_STEP_MALFORMED) {
       this->mark_failed(LOG_STR("Malformed init sequence"));
       return;
     }
-    uint8_t cmd = seq[index++];
-    uint8_t x = seq[index++];
-    if (x == DELAY_FLAG) {
-      ESP_LOGD(TAG, "Delay %dms", cmd);
-      delay(cmd);
-    } else {
-      uint8_t num_args = x & 0x7F;
-      if (len - index < num_args) {
-        this->mark_failed(LOG_STR("Malformed init sequence"));
-        return;
-      }
-      if (cmd == SLEEP_OUT) {
-        delay(120);  // NOLINT
-      }
-      const auto *ptr = seq + index;
-      char hex_buf[format_hex_pretty_size(MIPI_RGB_MAX_CMD_LOG_BYTES)];
-      ESP_LOGD(TAG, "Write command %02X, length %d, byte(s) %s", cmd, num_args,
-               format_hex_pretty_to(hex_buf, ptr, num_args, '.'));
-      index += num_args;
-      this->write_command_(cmd);
-      while (num_args-- != 0)
-        this->write_data_(*ptr++);
-      if (cmd == SLEEP_OUT)
-        delay(10);
+    if (step == display::INIT_SEQUENCE_STEP_DELAY) {
+      ESP_LOGD(TAG, "Delay %dms", entry.value);
+      delay(entry.value);
+      continue;
     }
+    const uint8_t cmd = entry.value;
+    if (cmd == SLEEP_OUT)
+      delay(120);  // NOLINT
+    char hex_buf[format_hex_pretty_size(MIPI_RGB_MAX_CMD_LOG_BYTES)];
+    ESP_LOGD(TAG, "Write command %02X, length %d, byte(s) %s", cmd, entry.count,
+             format_hex_pretty_to(hex_buf, entry.args, entry.count, '.'));
+    this->write_command_(cmd);
+    for (uint8_t i = 0; i < entry.count; i++)
+      this->write_data_(entry.args[i]);
+    if (cmd == SLEEP_OUT)
+      delay(10);
   }
   // this->spi_teardown();  // SPI not needed after this
   delay(10);

esphome/components/mipi_spi/display.py

@@ -33,7 +33,6 @@ from esphome.components.spi import CONF_SPI_MODE, TYPE_OCTAL, TYPE_QUAD, TYPE_SI
 import esphome.config_validation as cv
 from esphome.config_validation import ALLOW_EXTRA
 from esphome.const import (
-    CONF_AUTO_CLEAR_ENABLED,
     CONF_BRIGHTNESS,
     CONF_BUFFER_SIZE,
     CONF_COLOR_ORDER,
@@ -73,6 +72,10 @@ Model = mipi_spi_ns.enum("Model")
 PixelMode = mipi_spi_ns.enum("PixelMode")
 BusType = mipi_spi_ns.enum("BusType")
 
+# Matches INIT_SEQUENCE_MAX_ARGS, the flash copy buffer in mipi_spi.h
+INIT_SEQUENCE_MAX_ARGS = 128
+
+
 COLOR_ORDERS = {
     MODE_RGB: ColorOrder.COLOR_ORDER_RGB,
     MODE_BGR: ColorOrder.COLOR_ORDER_BGR,
@@ -216,7 +219,15 @@ def model_schema(config: ConfigType) -> cv.All | cv.Schema:
                     bus_mode, lower=True
                 ),
                 cv.Required(CONF_MODEL): cv.one_of(model.name, upper=True),
-                iseqconf: cv.ensure_list(map_sequence),
+                iseqconf: cv.ensure_list(
+                    cv.All(
+                        map_sequence,
+                        cv.Length(
+                            max=INIT_SEQUENCE_MAX_ARGS + 1,
+                            msg=f"An init sequence command can have at most {INIT_SEQUENCE_MAX_ARGS} data bytes",
+                        ),
+                    )
+                ),
                 cv.Optional(CONF_BUFFER_SIZE): cv.All(
                     cv.percentage, cv.Range(0.12, 1.0)
                 ),
@@ -290,8 +301,7 @@ def customise_schema(config: ConfigType) -> ConfigType:
         height,
         has_hardware_transform,
         byte_order=config[CONF_BYTE_ORDER],
-        has_writer=requires_buffer(config)
-        or config.get(CONF_AUTO_CLEAR_ENABLED) is True,
+        has_writer=display.config_has_writer(config),
         rotation=config.get(CONF_ROTATION, 0),
         draw_rounding=config.get(CONF_DRAW_ROUNDING, 0),
     )

esphome/components/mipi_spi/mipi_spi.h

@@ -7,12 +7,16 @@
 #include "esphome/components/spi/spi.h"
 #include "esphome/components/display/display.h"
 #include "esphome/components/display/display_color_utils.h"
+#include "esphome/components/display/init_sequence.h"
 #include "esphome/core/hal.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::mipi_spi {
 
+/// Largest argument count in one init command; display.py rejects longer ones.
+static constexpr size_t INIT_SEQUENCE_MAX_ARGS = 128;
+
 ESPHOME_LOG_TAG(TAG, "display.mipi_spi");
 
 // Maximum bytes to log for commands (truncated if larger)
@@ -48,7 +52,6 @@ static constexpr uint8_t MADCTL_XFLIP = 0x02;        // Mirror the display horiz
 static constexpr uint8_t MADCTL_YFLIP = 0x01;        // Mirror the display vertically
 static constexpr uint16_t MADCTL_FLIP_FLAG = 0x100;  // controller uses axis flip bits
 
-static constexpr uint8_t DELAY_FLAG = 0xFF;
 // store a 16 bit value in a buffer, big endian.
 static inline void put16_be(uint8_t *buf, uint16_t value) {
   buf[0] = value >> 8;
@@ -163,36 +166,23 @@ class MipiSpi : public display::Display,
 
     // need to know when the display is ready for SLPOUT command - will be 120ms after reset
     auto when = millis() + 120;
-    size_t index = 0;
-    const uint8_t *seq = this->init_sequence_;
-    const size_t len = this->init_sequence_len_;
-    while (index != len) {
-      if (len - index < 2) {
-        esph_log_e(TAG, "Malformed init sequence");
-        this->mark_failed();
+    display::InitSequenceReader reader(this->init_sequence_, this->init_sequence_len_);
+    display::InitSequenceEntry entry;
+    // The sequence is in flash, which SPI DMA (and ESP8266 byte loads) cannot read
+    uint8_t args[INIT_SEQUENCE_MAX_ARGS];
+    while (auto step = reader.next(entry, sizeof(args))) {
+      if (step == display::INIT_SEQUENCE_STEP_MALFORMED) {
+        this->mark_failed(LOG_STR("Malformed init sequence"));
         return;
       }
-      uint8_t cmd = progmem_read_byte(seq + index++);
-      uint8_t x = progmem_read_byte(seq + index++);
-      if (x == DELAY_FLAG) {
-        if (cmd == 0) {
-          cmd = clamp_at_least((int) (when - millis()), 0);
-        }
-        esph_log_d(TAG, "Delay %dms", cmd);
-        delay(cmd);
-      } else {
-        uint8_t num_args = x & 0x7F;
-        if (len - index < num_args) {
-          esph_log_e(TAG, "Malformed init sequence");
-          this->mark_failed();
-          return;
-        }
-        // The sequence is in flash, which SPI DMA (and ESP8266 byte loads) cannot read
-        uint8_t args[0x80];
-        progmem_memcpy(args, seq + index, num_args);
-        this->write_command_(cmd, args, num_args);
-        index += num_args;
+      if (step == display::INIT_SEQUENCE_STEP_DELAY) {
+        const uint8_t ms = entry.value != 0 ? entry.value : clamp_at_least((int) (when - millis()), 0);
+        esph_log_d(TAG, "Delay %dms", ms);
+        delay(ms);
+        continue;
       }
+      progmem_memcpy(args, entry.args, entry.count);
+      this->write_command_(entry.value, args, entry.count);
     }
     this->reset_params_();
     // Marks init as done, so later commands log at verbose level instead of debug

esphome/components/st7305/display.py

@@ -4,7 +4,6 @@ import pkgutil
 from esphome import pins
 import esphome.codegen as cg
 from esphome.components import display, spi
-from esphome.components.display import CONF_SHOW_TEST_CARD
 from esphome.components.mipi import (
     DriverChip,
     flatten_sequence,
@@ -13,16 +12,13 @@ from esphome.components.mipi import (
 )
 import esphome.config_validation as cv
 from esphome.const import (
-    CONF_AUTO_CLEAR_ENABLED,
     CONF_CS_PIN,
     CONF_DATA_RATE,
     CONF_DC_PIN,
     CONF_HEIGHT,
     CONF_ID,
     CONF_INIT_SEQUENCE,
-    CONF_LAMBDA,
     CONF_MODEL,
-    CONF_PAGES,
     CONF_RESET_PIN,
     CONF_ROTATION,
     CONF_WIDTH,
@@ -182,10 +178,7 @@ def customise_schema(config: ConfigType) -> ConfigType:
         config[CONF_HEIGHT],
         has_hardware_rotation=False,
         byte_order=cv.UNDEFINED,
-        has_writer=config.get(CONF_AUTO_CLEAR_ENABLED) is True
-        or config.get(CONF_PAGES) is not None
-        or config.get(CONF_LAMBDA) is not None
-        or config.get(CONF_SHOW_TEST_CARD) is True,
+        has_writer=display.config_has_writer(config),
         rotation=config.get(CONF_ROTATION, 0),
     )
     return config

esphome/components/st7305/st7305.cpp

@@ -56,33 +56,26 @@ void ST7305::reset_() {
 }
 
 void ST7305::send_init_sequence_() {
-  while (this->init_index_ < this->init_sequence_length_) {
-    if (this->init_sequence_length_ - this->init_index_ < 2) {
-      this->mark_failed(LOG_STR("Malformed init sequence"));
-      return;
-    }
-    const uint8_t command = progmem_read_byte(&this->init_sequence_[this->init_index_++]);
-    const uint8_t count = progmem_read_byte(&this->init_sequence_[this->init_index_++]);
-    if (count == 0xFF) {
-      // Resume the sequence after the delay instead of blocking the main loop.
-      this->set_timeout(STARTUP_TIMEOUT_ID, command, [this]() { this->send_init_sequence_(); });
-      return;
-    }
-    if (this->init_sequence_length_ - this->init_index_ < count) {
-      this->mark_failed(LOG_STR("Malformed init sequence"));
-      return;
-    }
+  display::InitSequenceEntry entry;
+  display::InitSequenceStep step;
+  while ((step = this->init_reader_.next(entry)) == display::INIT_SEQUENCE_STEP_COMMAND) {
     this->enable();
-    this->send_command_(command);
-    if (count != 0) {
+    this->send_command_(entry.value);
+    if (entry.count != 0) {
       this->dc_pin_->digital_write(true);
-      for (uint8_t i = 0; i < count; i++)
-        this->write_byte(progmem_read_byte(&this->init_sequence_[this->init_index_ + i]));
+      for (uint8_t i = 0; i < entry.count; i++)
+        this->write_byte(progmem_read_byte(entry.args + i));
     }
     this->disable();
-    this->init_index_ += count;
   }
-  this->finish_init_();
+  if (step == display::INIT_SEQUENCE_STEP_DELAY) {
+    // Resume the sequence after the delay instead of blocking the main loop.
+    this->set_timeout(STARTUP_TIMEOUT_ID, entry.value, [this]() { this->send_init_sequence_(); });
+  } else if (step == display::INIT_SEQUENCE_STEP_MALFORMED) {
+    this->mark_failed(LOG_STR("Malformed init sequence"));
+  } else {
+    this->finish_init_();
+  }
 }
 
 void ST7305::finish_init_() {

esphome/components/st7305/st7305.h

@@ -4,6 +4,7 @@
 #include <cstdint>
 
 #include "esphome/components/display/display_buffer.h"
+#include "esphome/components/display/init_sequence.h"
 #include "esphome/components/spi/spi.h"
 #include "esphome/core/component.h"
 #include "esphome/core/hal.h"
@@ -35,8 +36,7 @@ class ST7305 : public display::DisplayBuffer,
         row_start_(row_start),
         row_end_(row_end),
         buffer_length_(static_cast<size_t>(width) * static_cast<size_t>(height) / 8),
-        init_sequence_(init_sequence),
-        init_sequence_length_(init_sequence_length) {}
+        init_reader_(init_sequence, init_sequence_length) {}
 
   void setup() override;
   void update() override;
@@ -113,9 +113,7 @@ class ST7305 : public display::DisplayBuffer,
   uint8_t row_start_;
   uint8_t row_end_;
   size_t buffer_length_;
-  const uint8_t *init_sequence_;
-  size_t init_sequence_length_;
-  size_t init_index_{0};
+  display::InitSequenceReader init_reader_;
   bool ready_{false};
 
   int x_low_{0};

tests/component_tests/mipi_spi/test_init.py

@@ -93,6 +93,16 @@ def run_schema_validation(config: ConfigType) -> None:
             r"value must be a power of two for dictionary value @ data\['draw_rounding'\]",
             id="invalid_draw_rounding",
         ),
+        pytest.param(
+            {
+                "model": "custom",
+                "dc_pin": 18,
+                "dimensions": {"width": 320, "height": 240},
+                "init_sequence": [[0xE0] + [0x00] * 129],
+            },
+            r"at most 128 data bytes",
+            id="init_command_too_long",
+        ),
     ],
 )
 def test_basic_configuration_errors(
@@ -606,3 +616,19 @@ def test_identical_init_sequences_share_one_table(
     assert first is not None and second is not None
     assert first.group(1) == second.group(1)
     assert main_cpp.count("mipi_spi_init_sequence[] PROGMEM") == 1
+
+
+def test_init_command_at_buffer_limit(set_core_config: SetCoreConfigCallable) -> None:
+    """A command with exactly 128 data bytes fits the C++ copy buffer."""
+    set_core_config(
+        PlatformFramework.ESP32_IDF,
+        platform_data={KEY_BOARD: "esp32dev", KEY_VARIANT: VARIANT_ESP32},
+    )
+    run_schema_validation(
+        {
+            "model": "custom",
+            "dc_pin": 18,
+            "dimensions": {"width": 320, "height": 240},
+            "init_sequence": [[0xE0] + [0x00] * 128],
+        }
+    )