stm32cube: remove HAL Legacy definitions header from build files

Remove the HAL Legacy definitions header from most series using a dummy
replacement (shared by all series!) to ensure proper compilation despite
the missing file, and update the README of affected series to remove entry
documenting patches to the HAL Legacy definitions header.

While it at, get rid of all other legacy headers (can_legacy / eth_legacy)
which Zephyr never uses. This is purely cosmectic as these headers are
only used if the corresponding HAL module is enabled but Zephyr has never
enabled (and will never enable!) the CAN_LEGACY or ETH_LEGACY modules.

The STM32F7 and STM32U5 series are not modified and will continue to use
their current (patched) HAL Legacy definitions header: some drivers have
not been updated(!) and require legacy definitions to build...

Signed-off-by: Mathieu Choplain <mathieu.choplain-ext@st.com>

Author: mathieuchopstm

stm32cube/CMakeLists.txt

@@ -141,6 +141,10 @@ foreach(series ${supported_series})
     endif()
 
     add_subdirectory(${cube_dir})
+
+    # Remember the series' name for next steps
+    # (in the format of CONFIG_SOC_SERIES_<xxx>)
+    set(TARGET_SERIES ${series_to_upper})
   endif()
 endforeach()
 
@@ -151,3 +155,27 @@ endif()
 
 # Add the series-agnostic LL headers to include directories
 zephyr_include_directories(common_ll/include)
+
+# Legacy definitions header placeholder
+# (HAL1 only - not needed on HAL2 series)
+if(NOT CONFIG_STM32_HAL2)
+  # List of series containing buggy driver(s) which need some Legacy definitions.
+  # These series use their real Legacy definitions header - no placeholder.
+  #
+  # In a comment next to each series' name, please indicate:
+  # - which driver(s) are buggy and cause build issues
+  # - in parentheses, ST Internal Reference(s) tracking the issue(s)
+  set(legacy_dependent_series
+    # N.B.: no issue will occur if this list is empty
+    STM32F7X # HAL RCC (HAL1-19491)
+    STM32U5X # HAL PCD + LL USB (HAL1-9776)
+  )
+
+  list(FIND legacy_dependent_series ${TARGET_SERIES} index)
+  if(${index} EQUAL -1)
+    # Series not in exclude list: use the placeholder.
+    add_subdirectory(hal1_legacy_placeholder)
+  else()
+    # Target series uses its real header - don't use placeholder.
+  endif()
+endif()

stm32cube/hal1_legacy_placeholder/CMakeLists.txt

@@ -0,0 +1,22 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 STMicroelectronics
+# SPDX-License-Identifier: Apache-2.0
+
+# Adds the placeholder HAL1 Legacy definitions header to include path.
+#
+# Every HAL1 package contains a file "stm32_hal_legacy.h" filled
+# with aliases added whenever an HAL function or macro is renamed.
+# This is provided for backwards compatibility but we don't have
+# a need for it in Zephyr: the STM32-specific code is kept aligned
+# with the HAL's API even when it changes. In addition to being
+# useless, this header also contains `#define`s that conflict with
+# macros provided by Zephyr, causing build errors if unpatched.
+#
+# The Legacy definitions header is included as follows by one
+# of the HAL's most important headers ("stm32XXXxx_hal_def.h"):
+#
+#     #include "Legacy/stm32_hal_legacy.h"
+#
+# By adding the current directory in the include path, this directive
+# will include the placeholder file `./Legacy/stm32_hal_legacy.h` and
+# we can safely dispose of the real Legacy definitions header.
+zephyr_include_directories(.)

stm32cube/hal1_legacy_placeholder/Legacy/stm32_hal_legacy.h

@@ -0,0 +1,14 @@
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2026 STMicroelectronics
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Dummy replacement for the HAL1 Legacy definitions header.
+ *
+ * This file must be named `stm32_hal_legacy.h` and be inside a directory
+ * named `Legacy` because it is included by `stm32XXXxx_hal_def.h` using
+ * the following directive:
+ *
+ *      #include "Legacy/stm32_hal_legacy.h"
+ *
+ * Refer to `stm32cube/hal1_legacy/CMakeLists.txt` for more details.
+ */

stm32cube/stm32c0xx/README

@@ -40,8 +40,4 @@ Patch List:
     -Added stm32cube/stm32c0xx/drivers/include/stm32_assert.h
     -Removed unused stm32cube/stm32c0xx/drivers/include/stm32_assert_template.h
 
-   *Fix to remove PAGESIZE definition which conflicts with POSIX
-    Impacted files:
-     drivers/include/Legacy/stm32_hal_legacy.h
-
    See release_note.html from STM32Cube