[PATCH v15 3/6] reboot: add parsable tokens for power state change reasons

[Faruque Ansari <faruque.ansari@oss.qualcomm.com>]

psc_reason_to_str() returns human-readable labels that contain spaces
(e.g. "over temperature"). Those are fine for logs but unusable as
values in a space-separated sysfs list or as a write target.

Extend the single reason descriptor table with a stable, space-free
token next to the existing label, and add psc_reason_to_token() and
psc_reason_from_token() so consumers can emit and parse reasons without
inventing their own string table.

Co-developed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Faruque Ansari <faruque.ansari@oss.qualcomm.com>
Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>

Chnages v15
- Add Reviewed-by tags from Matti Vaittinen.

changes v12:
- new patch
---
 include/linux/reboot.h |  2 ++
 kernel/reboot.c        | 77 +++++++++++++++++++++++++++++++++++++++-----------
 2 files changed, 63 insertions(+), 16 deletions(-)

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 08a7549bbc40..4c5327dd7645 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -244,6 +244,8 @@ enum psc_reason {
 #define PSCR_MAX_REASON	(PSCR_REASON_COUNT - 1)
 
 const char *psc_reason_to_str(enum psc_reason reason);
+const char *psc_reason_to_token(enum psc_reason reason);
+int psc_reason_from_token(const char *token, enum psc_reason *reason);
 
 /**
  * enum hw_protection_action - Hardware protection action
diff --git a/kernel/reboot.c b/kernel/reboot.c
index d5a45db82c3d..e53fb31bad06 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -1084,34 +1084,79 @@ void set_psc_reason(enum psc_reason reason)
 }
 EXPORT_SYMBOL_GPL(set_psc_reason);
 
-static const char * const pscr_reason_strs[] = {
-	[PSCR_UNKNOWN]            = POWER_ON_REASON_UNKNOWN,
-	[PSCR_UNDER_VOLTAGE]      = POWER_ON_REASON_BROWN_OUT,
-	[PSCR_OVER_CURRENT]       = POWER_ON_REASON_OVER_CURRENT,
-	[PSCR_REGULATOR_FAILURE]  = POWER_ON_REASON_REGULATOR_FAILURE,
-	[PSCR_OVER_TEMPERATURE]   = POWER_ON_REASON_OVER_TEMPERATURE,
-	[PSCR_EC_PANIC]           = POWER_ON_REASON_EC_PANIC,
+/**
+ * struct psc_reason_desc - Descriptor for a power state change reason.
+ * @token: Stable, parsable identifier without spaces (e.g. "over-temperature").
+ *	   Suitable for use in sysfs values and as a user/kernel contract.
+ * @label: Human-readable description (e.g. "over temperature"), for logs.
+ */
+struct psc_reason_desc {
+	const char *token;
+	const char *label;
+};
+
+static const struct psc_reason_desc psc_reason_descs[] = {
+	[PSCR_UNKNOWN]		 = { "unknown",		  POWER_ON_REASON_UNKNOWN },
+	[PSCR_UNDER_VOLTAGE]	 = { "under-voltage",	  POWER_ON_REASON_BROWN_OUT },
+	[PSCR_OVER_CURRENT]	 = { "over-current",	  POWER_ON_REASON_OVER_CURRENT },
+	[PSCR_REGULATOR_FAILURE] = { "regulator-failure", POWER_ON_REASON_REGULATOR_FAILURE },
+	[PSCR_OVER_TEMPERATURE]	 = { "over-temperature",  POWER_ON_REASON_OVER_TEMPERATURE },
+	[PSCR_EC_PANIC]		 = { "ec-panic",	  POWER_ON_REASON_EC_PANIC },
 };
 
 /**
- * psc_reason_to_str - Converts a power state change reason enum to a string.
- * @reason: The `psc_reason` enum value to be converted.
- *
- * This function provides a human-readable string representation of the power
- * state change reason, making it easier to interpret logs and debug messages.
+ * psc_reason_to_str - Human-readable label for a power state change reason.
+ * @reason: The `psc_reason` value to convert.
  *
- * Return:
- * - A string corresponding to the given `psc_reason` value.
- * - `"Invalid"` if the value is not recognized.
+ * Return: The label string, or "Invalid" if @reason is out of range. For a
+ * stable, parsable form use psc_reason_to_token() instead.
  */
 const char *psc_reason_to_str(enum psc_reason reason)
 {
 	if (reason < 0 || reason >= PSCR_REASON_COUNT)
 		return "Invalid";
-	return pscr_reason_strs[reason];
+	return psc_reason_descs[reason].label;
 }
 EXPORT_SYMBOL_GPL(psc_reason_to_str);
 
+/**
+ * psc_reason_to_token - Stable, parsable token for a power state change reason.
+ * @reason: The `psc_reason` value to convert.
+ *
+ * Return: The token string (no spaces), or "invalid" if @reason is out of
+ * range. Round-trips with psc_reason_from_token().
+ */
+const char *psc_reason_to_token(enum psc_reason reason)
+{
+	if (reason < 0 || reason >= PSCR_REASON_COUNT)
+		return "invalid";
+	return psc_reason_descs[reason].token;
+}
+EXPORT_SYMBOL_GPL(psc_reason_to_token);
+
+/**
+ * psc_reason_from_token - Parse a reason token into a `psc_reason` value.
+ * @token: A token as returned by psc_reason_to_token(). A trailing newline is
+ *	   tolerated.
+ * @reason: Output; set on success.
+ *
+ * Return: 0 on success or -EINVAL if @token matches no known reason.
+ */
+int psc_reason_from_token(const char *token, enum psc_reason *reason)
+{
+	int i;
+
+	for (i = 0; i < PSCR_REASON_COUNT; i++) {
+		if (sysfs_streq(token, psc_reason_descs[i].token)) {
+			*reason = i;
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(psc_reason_from_token);
+
 /**
  * __hw_protection_trigger - Trigger an emergency system shutdown or reboot
  *

-- 
2.34.1