Add NULL checks to per-frame allocations

Cover the per-frame allocations in do_update, clear_screen, and
dcs_lcd_draw_buffer across all four ESP32 drivers. On failure,
skip the frame with a log line and free any already-acquired
resources. The caller's reply has already been sent at enqueue
time (see the prior pre-ack commit), so there is no reply
obligation.

Also fix an oled do_update early-return on i2c_driver_acquire
failure that leaked both `items` and `buf`.

Init-time allocations in *_create_port / display_init /
display_spi_init remain unchecked; context-teardown-on-init-
failure is tracked as a separate follow-up.

Author: bettio

dcs_lcd_commands.c

@@ -20,8 +20,11 @@
 
 #include "dcs_lcd_commands.h"
 
+#include <stdio.h>
 #include <stdlib.h>
 
+#include <utils.h>
+
 #include <freertos/FreeRTOS.h>
 #include <freertos/task.h>
 
@@ -62,6 +65,11 @@ void dcs_lcd_draw_buffer(struct SPIDCBus *bus, const struct DCSLCDScreen *screen
     if (pixel_bytes == 2) {
         int buf_pixel_size = (dest_size > 1024) ? 1024 : dest_size;
         uint16_t *tmpbuf = heap_caps_malloc(buf_pixel_size * sizeof(uint16_t), MALLOC_CAP_DMA);
+        if (UNLIKELY(!tmpbuf)) {
+            fprintf(stderr, "dcs_lcd_draw_buffer: failed to alloc tmpbuf (rgb565)\n");
+            spi_device_release_bus(bus->spi_disp.handle);
+            return;
+        }
 
         for (int i = 0; i < chunks; i++) {
             const uint16_t *data_b = data + 1024 * i;
@@ -86,6 +94,11 @@ void dcs_lcd_draw_buffer(struct SPIDCBus *bus, const struct DCSLCDScreen *screen
         // ILI9488: RGB565 -> RGB888 (3 bytes/pixel).
         const int chunk_pixels = 512;
         uint8_t *tmpbuf = heap_caps_malloc(chunk_pixels * 3, MALLOC_CAP_DMA);
+        if (UNLIKELY(!tmpbuf)) {
+            fprintf(stderr, "dcs_lcd_draw_buffer: failed to alloc tmpbuf (rgb888)\n");
+            spi_device_release_bus(bus->spi_disp.handle);
+            return;
+        }
 
         int i = 0;
         while (i < dest_size) {

dcs_lcd_display_driver.c

@@ -143,6 +143,10 @@ static void do_update(Context *ctx, term display_list)
     int len = term_list_length(display_list, &proper);
 
     BaseDisplayItem *items = malloc(sizeof(BaseDisplayItem) * len);
+    if (UNLIKELY(!items)) {
+        fprintf(stderr, "do_update: failed to alloc items\n");
+        return;
+    }
 
     term t = display_list;
     for (int i = 0; i < len; i++) {

epaper_display_driver.c

@@ -186,6 +186,10 @@ static void do_update(Context *ctx, term display_list)
     int len = term_list_length(display_list, &proper);
 
     BaseDisplayItem *items = malloc(sizeof(BaseDisplayItem) * len);
+    if (UNLIKELY(!items)) {
+        fprintf(stderr, "do_update: failed to alloc items\n");
+        return;
+    }
 
     term t = display_list;
     for (int i = 0; i < len; i++) {
@@ -203,6 +207,11 @@ static void do_update(Context *ctx, term display_list)
     spi_dc_write_command(&driver->bus, 0x10);
 
     uint8_t *buf = heap_caps_malloc(screen_width / 2, MALLOC_CAP_DMA);
+    if (UNLIKELY(!buf)) {
+        fprintf(stderr, "do_update: failed to alloc buf\n");
+        display_items_delete(items, len);
+        return;
+    }
     memset(buf, 0x11, screen_width / 2);
 
     bool transaction_in_progress = false;
@@ -294,6 +303,10 @@ static void clear_screen(Context *ctx, int color)
     spi_dc_write_command(&driver->bus, 0x10);
 
     uint8_t *buf = heap_caps_malloc(screen_width / 2, MALLOC_CAP_DMA);
+    if (UNLIKELY(!buf)) {
+        fprintf(stderr, "clear_screen: failed to alloc buf\n");
+        return;
+    }
 
     bool transaction_in_progress = false;
 

memory_display_driver.c

@@ -98,6 +98,10 @@ static void do_update(Context *ctx, term display_list)
     int len = term_list_length(display_list, &proper);
 
     BaseDisplayItem *items = malloc(sizeof(BaseDisplayItem) * len);
+    if (UNLIKELY(!items)) {
+        fprintf(stderr, "do_update: failed to alloc items\n");
+        return;
+    }
 
     term t = display_list;
     for (int i = 0; i < len; i++) {

oled_display_driver.c

@@ -100,6 +100,10 @@ static void do_update(Context *ctx, term display_list)
     int len = term_list_length(display_list, &proper);
 
     BaseDisplayItem *items = malloc(sizeof(BaseDisplayItem) * len);
+    if (UNLIKELY(!items)) {
+        fprintf(stderr, "do_update: failed to alloc items\n");
+        return;
+    }
 
     term t = display_list;
     for (int i = 0; i < len; i++) {
@@ -113,11 +117,18 @@ static void do_update(Context *ctx, term display_list)
 
     int memsize = (DISPLAY_WIDTH * (PAGE_HEIGHT + 1)) / sizeof(uint8_t);
     uint8_t *buf = malloc(memsize);
+    if (UNLIKELY(!buf)) {
+        fprintf(stderr, "do_update: failed to alloc buf\n");
+        display_items_delete(items, len);
+        return;
+    }
     memset(buf, 0, memsize);
 
     i2c_port_t i2c_num;
     if (i2c_driver_acquire(driver->i2c_host, &i2c_num, ctx->global) != I2CAcquireOk) {
         fprintf(stderr, "Invalid I2C peripheral\n");
+        free(buf);
+        display_items_delete(items, len);
         return;
     }