[PATCH v3 1/4] power: supply: Add registration init callback

[Vincent Cloutier <vincent.cloutier@icloud.com>]

From: Vincent Cloutier <vincent@cloutier.co>

Some battery drivers need to consume monitored-battery data before their
power_supply is visible. That lets them prepare hardware configuration from
parsed battery information without racing userspace exposure.

power_supply_get_battery_info() already runs in
__power_supply_register() for battery devices before device_add(). Add an
optional descriptor init callback after driver data and battery info are
available. The callback runs in sleepable process context while the power
supply is still unpublished.

Require callbacks to return zero or a negative errno. Defensively reject
positive returns so registration cannot return an invalid error pointer.

Assisted-by: OpenCode:gpt-5.6-sol
Signed-off-by: Vincent Cloutier <vincent@cloutier.co>
---
 drivers/power/supply/power_supply_core.c | 8 ++++++++
 include/linux/power_supply.h             | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
index 2532e221b2e1..3ed4c253706f 100644
--- a/drivers/power/supply/power_supply_core.c
+++ b/drivers/power/supply/power_supply_core.c
@@ -1624,6 +1624,14 @@ __power_supply_register(struct device *parent,
 	init_rwsem(&psy->extensions_sem);
 	INIT_LIST_HEAD(&psy->extensions);
 
+	if (desc->init) {
+		rc = desc->init(psy);
+		if (WARN_ON_ONCE(rc > 0))
+			rc = -EINVAL;
+		if (rc)
+			goto check_supplies_failed;
+	}
+
 	rc = device_add(dev);
 	if (rc)
 		goto device_add_failed;
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index 7a5e4c3242a0..6042f5e1fdc2 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -281,6 +281,14 @@ struct power_supply_desc {
 	int (*property_is_writeable)(struct power_supply *psy,
 				     enum power_supply_property psp);
 	void (*external_power_changed)(struct power_supply *psy);
+	/*
+	 * Optional registration-time initialization. This runs in sleepable
+	 * process context after driver data and any battery info are available,
+	 * but before the device is added. The callback must not publish changes
+	 * because registration is not complete. Return 0 on success or a negative
+	 * errno on failure.
+	 */
+	int (*init)(struct power_supply *psy);
 
 	/*
 	 * Set if thermal zone should not be created for this power supply.
-- 
2.55.0