[RESEND PATCH 2/3] power: supply: max17040: derive status from an online supplier

[Hugo Karlsson]

The MAX1704x gauges cannot tell whether the cell is charging, so
POWER_SUPPLY_PROP_STATUS is taken from a supplier. A supplier that only
reports input power, such as a gpio-charger without a charge-status
GPIO, has no STATUS property, and the battery then reports
POWER_SUPPLY_STATUS_UNKNOWN even though the core knows whether it is
being supplied.

This is the case on the Geekworm X1202/X1206 UPS boards for the
Raspberry Pi 5, which pair a MAX1704x gauge with a GPIO that signals input
power.

When no supplier reports a status, fall back to
power_supply_am_i_supplied(): report Discharging when no supplier is
online, Full when one is online and the gauge reads 100 %, and Charging
otherwise. Keep Unknown when the battery has no supplier at all.

Also notify userspace when a supplier changes, so the status follows
the charger being plugged in or removed without waiting for the next
SOC change.

Assisted-by: Claude:claude-opus-5-5 [Claude Code]
Signed-off-by: Hugo Karlsson <huggek@xxxxxxxxxxx>
---
 drivers/power/supply/max17040_battery.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/power/supply/max17040_battery.c b/drivers/power/supply/max17040_battery.c
index 4cb26eca56..d93c3daebb 100644
--- a/drivers/power/supply/max17040_battery.c
+++ b/drivers/power/supply/max17040_battery.c
@@ -228,6 +228,26 @@ static int max17040_get_online(struct max17040_chip *chip)
 	return 1;
 }
 
+/*
+ * Used when no supplier reports a status, e.g. a gpio-charger that only
+ * signals input power: derive the status from whether a supplier is online.
+ */
+static int max17040_get_supplied_status(struct power_supply *psy,
+					struct max17040_chip *chip)
+{
+	int ret;
+
+	ret = power_supply_am_i_supplied(psy);
+	if (ret < 0)
+		return POWER_SUPPLY_STATUS_UNKNOWN;
+	if (!ret)
+		return POWER_SUPPLY_STATUS_DISCHARGING;
+	if (max17040_get_soc(chip) >= 100)
+		return POWER_SUPPLY_STATUS_FULL;
+
+	return POWER_SUPPLY_STATUS_CHARGING;
+}
+
 static int max17040_get_of_data(struct max17040_chip *chip)
 {
 	struct device *dev = &chip->client->dev;
@@ -423,7 +443,7 @@ static int max17040_get_property(struct power_supply *psy,
 	case POWER_SUPPLY_PROP_STATUS:
 		ret = power_supply_get_property_from_supplier(psy, psp, val);
 		if (ret == -ENODEV)
-			val->intval = POWER_SUPPLY_STATUS_UNKNOWN;
+			val->intval = max17040_get_supplied_status(psy, chip);
 		else if (ret)
 			return ret;
 		break;
@@ -467,6 +487,7 @@ static const struct power_supply_desc max17040_battery_desc = {
 	.get_property		= max17040_get_property,
 	.set_property		= max17040_set_property,
 	.property_is_writeable  = max17040_prop_writeable,
+	.external_power_changed	= power_supply_changed,
 	.properties		= max17040_battery_props,
 	.num_properties		= ARRAY_SIZE(max17040_battery_props),
 };
-- 
2.55.0.windows.5