init: drop init_fn union

Device init function is no longer taken from `struct init_entry`, so
there's no need to keep such union.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

include/zephyr/init.h

@@ -49,43 +49,6 @@ extern "C" {
 
 struct device;
 
-/**
- * @brief Initialization function for init entries.
- *
- * Init entries support both the system initialization and the device
- * APIs. Each API has its own init function signature; hence, we have a
- * union to cover both.
- */
-union init_function {
-	/**
-	 * System initialization function.
-	 *
-	 * @retval 0 On success
-	 * @retval -errno If init fails.
-	 */
-	int (*sys)(void);
-	/**
-	 * Device initialization function.
-	 *
-	 * @param dev Device instance.
-	 *
-	 * @retval 0 On success
-	 * @retval -errno If device initialization fails.
-	 */
-	int (*dev)(const struct device *dev);
-#ifdef CONFIG_DEVICE_MUTABLE
-	/**
-	 * Device initialization function (rw).
-	 *
-	 * @param dev Device instance.
-	 *
-	 * @retval 0 On success
-	 * @retval -errno If device initialization fails.
-	 */
-	int (*dev_rw)(struct device *dev);
-#endif
-};
-
 /**
  * @brief Structure to store initialization entry information.
  *
@@ -101,8 +64,11 @@ union init_function {
  * @endinternal
  */
 struct init_entry {
-	/** Initialization function. */
-	union init_function init_fn;
+	/**
+	 * If the init function belongs to a SYS_INIT, this field stored the
+	 * initialization function, otherwise it is set to NULL.
+	 */
+	int (*init_fn)(void);
 	/**
 	 * If the init entry belongs to a device, this fields stores a
 	 * reference to it, otherwise it is set to NULL.
@@ -151,39 +117,6 @@ struct init_entry {
 	__attribute__((__section__(                                           \
 		".z_init_" #level STRINGIFY(prio)"_" STRINGIFY(sub_prio)"_")))
 
-
-/* Designated initializers where added to C in C99. There were added to
- * C++ 20 years later in a much more restricted form. C99 allows many
- * variations: out of order, mix of designated and not, overlap,
- * override,... but C++ allows none of these. See differences detailed
- * in the P0329R0.pdf C++ proposal.
- * Note __STDC_VERSION__ is undefined when compiling C++.
- */
-#if defined(__STDC_VERSION__) && (__STDC_VERSION__) < 201100
-
-/* Anonymous unions require C11. Some pre-C11 gcc versions have early
- * support for anonymous unions but they require these braces when
- * combined with C99 designated initializers, see longer discussion in
- * #69411.
- * These braces are compatible with any C version but not with C++20.
- */
-#  define Z_INIT_SYS_INIT_DEV_NULL  { .dev = NULL }
-
-#else
-
-/* When using -std=c++20 or higher, g++ (v12.2.0) reject braces for
- * initializing anonymous unions because it is technically a mix of
- * designated and not designated initializers which is not allowed in
- * C++. Interestingly, the _same_ g++ version does accept the braces above
- * when using -std=c++17 or lower!
- * The tests/lib/cpp/cxx/ added by commit 3d9c428d57bf invoke the C++
- * compiler with a range of different `-std=...` parameters without needing
- * any manual configuration.
- */
-#  define Z_INIT_SYS_INIT_DEV_NULL    .dev = NULL
-
-#endif
-
 /** @endcond */
 
 /**
@@ -238,8 +171,7 @@ struct init_entry {
 #define SYS_INIT_NAMED(name, init_fn_, level, prio)                                       \
 	static const Z_DECL_ALIGN(struct init_entry)                                      \
 		Z_INIT_ENTRY_SECTION(level, prio, 0) __used __noasan                      \
-		Z_INIT_ENTRY_NAME(name) = {.init_fn = {.sys = (init_fn_)},                \
-			Z_INIT_SYS_INIT_DEV_NULL}
+		Z_INIT_ENTRY_NAME(name) = {.init_fn = (init_fn_)}                         \
 
 /** @} */
 

kernel/init.c

@@ -367,7 +367,7 @@ static void z_sys_init_run_level(enum init_level level)
 		if (dev != NULL) {
 			result = do_device_init(dev);
 		} else {
-			result = entry->init_fn.sys();
+			result = entry->init_fn();
 		}
 		sys_trace_sys_init_exit(entry, level, result);
 	}