fix(nrf52): align external QSPI DMA buffers

scripts/nrf52_qspi_dma_fix.py

@@ -0,0 +1,77 @@
+"""Align reviewed CustomLFS QSPI buffers in private build copies.
+
+The nRF52840 QSPI driver rejects non-word-aligned EasyDMA addresses. uint8_t
+static arrays only guarantee byte alignment; unrelated code/layout changes
+can silently break mounting. Retain all three original pools and their size,
+allocation lifetime, callbacks and filesystem behavior. Never edit libdeps.
+"""
+import hashlib
+from pathlib import Path
+
+SOURCE_SHA256 = 'b36b21e52480d1c4e56a235d0d9e3d72c4f2141a9d6c46e1781d64dc08180540'
+PATCHED_SHA256 = '1d68cf61699e3988c59d9c7e87efb5479caf5391a847bab6c0e502b5593e35dd'
+HEADERS = {
+    'CustomLFS_QSPIFlash.h': '941596581f9f745b546e60e77e5738548b891d38f1a2830160a50646d6cf7486',
+    'CustomLFS.h': '65a2efcf699d6069dd68fd4f19b856a9e0573bda61fa3fc20568951b8d31f52d',
+}
+ORIGINAL_BUFFERS = '''  static uint8_t read_buffer[256];
+  static uint8_t prog_buffer[256];
+  static uint8_t lookahead_buffer[32];'''
+PATCHED_BUFFERS = '''  // QSPI EasyDMA and the LittleFS word bitmap require word alignment.
+  alignas(uint32_t) static uint8_t read_buffer[256];
+  alignas(uint32_t) static uint8_t prog_buffer[256];
+  alignas(uint32_t) static uint8_t lookahead_buffer[32];'''
+
+
+def digest(source):
+    return hashlib.sha256(source.encode('ascii')).hexdigest()
+
+
+def patched_source(source):
+    source = source.replace('\r\n', '\n')
+    fingerprint = digest(source)
+    if fingerprint == PATCHED_SHA256:
+        return source
+    if fingerprint != SOURCE_SHA256 or source.count(ORIGINAL_BUFFERS) != 1:
+        raise RuntimeError('nRF52 QSPI DMA fix: changed reviewed CustomLFS source; review dependency update')
+    result = source.replace(ORIGINAL_BUFFERS, PATCHED_BUFFERS, 1)
+    if digest(result) != PATCHED_SHA256:
+        raise RuntimeError('nRF52 QSPI DMA fix: unexpected transform result')
+    return result
+
+
+def write_if_changed(path, content):
+    if not path.exists() or path.read_text(encoding='ascii') != content:
+        path.write_text(content, encoding='ascii')
+
+
+def replace_qspi_source(build_env, node):
+    source = Path(node.srcnode().get_abspath())
+    if source.name != 'CustomLFS_QSPIFlash.cpp' or source.parent.name != 'src':
+        return node
+    patched = patched_source(source.read_text(encoding='ascii'))
+    headers = {}
+    for name, expected in HEADERS.items():
+        try:
+            header = (source.parent / name).read_text(encoding='ascii').replace('\r\n', '\n')
+        except (OSError, UnicodeError) as error:
+            raise RuntimeError('nRF52 QSPI DMA fix: missing reviewed header') from error
+        if digest(header) != expected:
+            raise RuntimeError('nRF52 QSPI DMA fix: changed reviewed header; review dependency update')
+        headers[name] = header
+    destination = Path(build_env.subst('$BUILD_DIR')) / 'patched-nrf52-qspi' / source.name
+    destination.parent.mkdir(parents=True, exist_ok=True)
+    # Quoted includes bind both headers to this reviewed dependency version.
+    for name, header in headers.items():
+        write_if_changed(destination.parent / name, header)
+    write_if_changed(destination, patched)
+    return build_env.File(str(destination))
+
+
+def install(build_env):
+    build_env.AddBuildMiddleware(replace_qspi_source, '*CustomLFS_QSPIFlash.cpp')
+
+
+if 'Import' in globals():
+    Import('env')
+    install(env)