fix: guard against null DMA buffer in Panel_AMOLED_Framebuffer::display()#211
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lovyan03 merged 6 commits intoJul 7, 2026
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The previous change to namespace alias broke direct font calls in user scripts. Reverting to ensure users don't need to manually update their font references.
Panel_AMOLED_Framebuffer::display() guards a null _frame_buffer but not the per-line DMA buffers from getDMABuffer(), which return nullptr when the DMA-capable internal heap is transiently exhausted. The subsequent memcpy into a null pointer faults (StoreProhibited). Skip the flush and leave the dirty range intact so the next display() retries once memory frees. A new per-instance _dma_oom flag edge-logs the condition (ESP_LOGW) and its recovery (ESP_LOGI) without per-frame spam. Reproduced and fixed on an M5Stack StopWatch (466x466 CO5300): under memory pressure the small per-line alloc fails while a full-screen buffer is cached, and any transient (e.g. a TLS reconnect) tips it over. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Panel_AMOLED_Framebuffer::display() guards a null _frame_buffer but not the per-line DMA buffers from getDMABuffer(), which return nullptr when the DMA-capable internal heap is transiently exhausted. The subsequent memcpy into a null pointer faults (StoreProhibited). Skip the flush and leave the dirty range intact so the next display() retries once memory frees. A new per-instance _dma_oom flag edge-logs the condition (ESP_LOGW) and its recovery (ESP_LOGI) without per-frame spam. Ported from m5stack/M5GFX#211, originally authored by Zac Anderson. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Follow-up to #211: apply the same null guard to the three getDMABuffer() call sites in writeImage(), via a shared get_dma_buffer_checked() helper with edge-triggered logging.
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Problem
Panel_AMOLED_Framebuffer::display()obtains two per-line DMA buffers fromgetDMABuffer()andmemcpys framebuffer data into them each line, but only null-checks_frame_buffer— not the DMA buffers. When the DMA-capable internal heap is exhausted (transient memory pressure),getDMABuffer()returnsnullptr, so the flushmemcpys into a null pointer and the device panics (StoreProhibited, write to0x00000000).Fix
Skip the flush if either DMA buffer is null, leaving the dirty rectangle (
_range_mod) intact so the nextdisplay()retries once memory frees. A per-instance flag edge-logs the condition (ESP_LOGW) and its recovery (ESP_LOGI) without per-frame spam.Minimal repro
heap_caps_get_largest_free_block(MALLOC_CAP_DMA)is below one display line's bytes (panel_width * bytes_per_pixel).Without this patch it panics on the null
memcpy; with it the frame is skipped and redraws once memory is freed.Notes
The same unchecked
getDMABuffer()pattern also appears in thewriteImage*pixel-copy paths; this PR scopes to the framebuffer flush we could reproduce and verify — glad to extend it to a full sweep if you'd prefer.Disclosure on process: this patch was authored by an AI coding agent and reviewed by a human; the bug was discovered and the fix validated on hardware through human + agent collaboration (fault-injection confirming the null path panics without the guard and is safely skipped with it). Happy to open a tracking issue first if that's your preference.