drivers: regulator: fix variable sized voltages fallback

Fix build issue reported by Clang on variable size field desc
not being located at the end of struct voltages_fallback. The
error was reported with a trace message like below:

core/include/drivers/regulator.h:118:4: warning: field 'voltages_fallback' with variable sized type 'struct voltages_fallback' not at the end of a struct or class is a GNU extension [-Wgnu-variable-sized-type-not-at-end]
        } voltages_fallback;
          ^
core/drivers/regulator/regulator_fixed.c:27:19: warning: field 'regulator' with variable sized type 'struct regulator' not at the end of a struct or class is a GNU extension [-Wgnu-variable-sized-type-not-at-end]
        struct regulator regulator;
                         ^
2 warnings generated.

API function regulator_supported_voltages() asserts that
struct regulator_voltages and struct voltages_fallback do match.

By the way, remove empty line in struct regulator_voltages inline
description comment.

Fixes: 43c155b ("drivers: regulator: list supported levels")
Signed-off-by: Etienne Carriere <[email protected]>

core/drivers/regulator/regulator.c

@@ -215,6 +215,14 @@ TEE_Result regulator_set_voltage(struct regulator *regulator, int level_uv)
 TEE_Result regulator_supported_voltages(struct regulator *regulator,
 					struct regulator_voltages **voltages)
 {
+	struct voltages_fallback __unused fb = { };
+
+	static_assert(offsetof(struct regulator_voltages, type) ==
+		      offsetof(struct voltages_fallback, type) &&
+		      offsetof(struct regulator_voltages, num_levels) ==
+		      offsetof(struct voltages_fallback, num_levels) &&
+		      sizeof(*(*voltages)->entries) == sizeof(*fb.levels));
+
 	assert(regulator && voltages);
 
 	if (regulator->ops->supported_voltages) {
@@ -227,13 +235,14 @@ TEE_Result regulator_supported_voltages(struct regulator *regulator,
 			return res;
 	}
 
-	*voltages = &regulator->voltages_fallback.desc;
+	*voltages = (void *)(vaddr_t)&regulator->voltages_fallback;
 
 	return TEE_SUCCESS;
 }
 
 TEE_Result regulator_register(struct regulator *regulator)
 {
+	struct regulator_voltages __unused voltages = { };
 	TEE_Result res = TEE_SUCCESS;
 	int min_uv = 0;
 	int max_uv = 0;
@@ -272,11 +281,11 @@ TEE_Result regulator_register(struct regulator *regulator)
 
 	/* Preset voltage list in case ops::supported_voltages is NULL */
 	if (regulator->min_uv == regulator->max_uv) {
-		regulator->voltages_fallback.desc.type = VOLTAGE_TYPE_FULL_LIST;
-		regulator->voltages_fallback.desc.num_levels = 1;
+		regulator->voltages_fallback.type = VOLTAGE_TYPE_FULL_LIST;
+		regulator->voltages_fallback.num_levels = 1;
 		regulator->voltages_fallback.levels[0] = regulator->min_uv;
 	} else {
-		regulator->voltages_fallback.desc.type = VOLTAGE_TYPE_INCREMENT;
+		regulator->voltages_fallback.type = VOLTAGE_TYPE_INCREMENT;
 		regulator->voltages_fallback.levels[0] = regulator->min_uv;
 		regulator->voltages_fallback.levels[1] = regulator->max_uv;
 		regulator->voltages_fallback.levels[2] = 1;

core/include/drivers/regulator.h

@@ -71,14 +71,25 @@ enum voltage_type {
  * @type: Type of level description
  * @num_levels: Number of cells of @entries when @type is VOLTAGE_TYPE_FULL_LIST
  * @entries: Voltage level information in uV
- *
  */
 struct regulator_voltages {
 	enum voltage_type type;
 	size_t num_levels;
 	int entries[];
 };
 
+/*
+ * struct struct voltages_fallback - Default Voltage levels description
+ * @type: Type of level description
+ * @num_levels: Number of cells of @entries when @type is VOLTAGE_TYPE_FULL_LIST
+ * @levels: Voltage level information in uV
+ */
+struct voltages_fallback {
+	enum voltage_type type;
+	size_t num_levels;
+	int levels[3];
+};
+
 /*
  * struct regulator - A regulator instance
  * @ops: Operation handlers for the regulator
@@ -107,10 +118,7 @@ struct regulator {
 	unsigned int flags;
 	unsigned int refcount;
 	struct mutex lock;	/* Concurrent access protection */
-	struct voltages_fallback {
-		struct regulator_voltages desc;
-		int levels[3];
-	} voltages_fallback;
+	struct voltages_fallback voltages_fallback;
 	size_t levels_count_fallback;
 	SLIST_ENTRY(regulator) link;
 };