[nrf fromtree] pm: states: add enum-string conversion helpers

Add two helper functions to convert power management states between
enum and string:

- pm_state_to_string()
- pm_state_from_string()

Signed-off-by: Yongxu Wang <[email protected]>
(cherry picked from commit 8767cec)

Author: yongxu-wang15

include/zephyr/pm/state.h

@@ -9,6 +9,7 @@
 
 #include <zephyr/sys/util.h>
 #include <zephyr/devicetree.h>
+#include <errno.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -382,6 +383,26 @@ uint8_t pm_state_cpu_get_all(uint8_t cpu, const struct pm_state_info **states);
  * @return Pointer to the power state structure or NULL if state is not found.
  */
 const struct pm_state_info *pm_state_get(uint8_t cpu, enum pm_state state, uint8_t substate_id);
+
+/**
+ * @brief Convert a pm_state enum value to its string representation.
+ *
+ * @param state Power state.
+ *
+ * @return A constant string representing the state.
+ */
+const char *pm_state_to_str(enum pm_state state);
+
+
+/**
+ * @brief Parse a string and convert it to a pm_state enum value.
+ *
+ * @param name Input string (e.g., "suspend-to-ram").
+ * @param out Pointer to store the parsed pm_state value.
+ *
+ * @return 0 on success, -EINVAL if the string is invalid or NULL.
+ */
+int pm_state_from_str(const char *name, enum pm_state *out);
 /**
  * @}
  */

subsys/pm/state.c

@@ -107,3 +107,48 @@ const struct pm_state_info *pm_state_get(uint8_t cpu, enum pm_state state, uint8
 
 	return NULL;
 }
+
+const char *pm_state_to_str(enum pm_state state)
+{
+	switch (state) {
+	case PM_STATE_ACTIVE:
+		return "active";
+	case PM_STATE_RUNTIME_IDLE:
+		return "runtime-idle";
+	case PM_STATE_SUSPEND_TO_IDLE:
+		return "suspend-to-idle";
+	case PM_STATE_STANDBY:
+		return "standby";
+	case PM_STATE_SUSPEND_TO_RAM:
+		return "suspend-to-ram";
+	case PM_STATE_SUSPEND_TO_DISK:
+		return "suspend-to-disk";
+	case PM_STATE_SOFT_OFF:
+		return "soft-off";
+	default:
+		return "UNKNOWN";
+	}
+}
+
+int pm_state_from_str(const char *name, enum pm_state *out)
+{
+	if (strcmp(name, "active") == 0) {
+		*out = PM_STATE_ACTIVE;
+	} else if (strcmp(name, "runtime-idle") == 0) {
+		*out = PM_STATE_RUNTIME_IDLE;
+	} else if (strcmp(name, "suspend-to-idle") == 0) {
+		*out = PM_STATE_SUSPEND_TO_IDLE;
+	} else if (strcmp(name, "standby") == 0) {
+		*out = PM_STATE_STANDBY;
+	} else if (strcmp(name, "suspend-to-ram") == 0) {
+		*out = PM_STATE_SUSPEND_TO_RAM;
+	} else if (strcmp(name, "suspend-to-disk") == 0) {
+		*out = PM_STATE_SUSPEND_TO_DISK;
+	} else if (strcmp(name, "soft-off") == 0) {
+		*out = PM_STATE_SOFT_OFF;
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}