[PATCH 1/2] power: supply: sbs-battery: Reject all-zero readings as battery absent

[LI Qingwu]

The driver reports battery present when status register read succeeds,
without checking the actual register values. Some systems return all
zeros when no battery is connected, causing false presence detection.

Add validation: when status reads zero, cross-check voltage and capacity.
Report battery absent only if all three registers return zero.

Tested on i.MX 8M Plus platform with SBS-compliant battery.

Signed-off-by: LI Qingwu <Qing-wu.Li@xxxxxxxxxxxxxxxxxxxxxxx>
---
 drivers/power/supply/sbs-battery.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/power/supply/sbs-battery.c b/drivers/power/supply/sbs-battery.c
index 943c82ee978f..0b9ecfc1f3f7 100644
--- a/drivers/power/supply/sbs-battery.c
+++ b/drivers/power/supply/sbs-battery.c
@@ -594,9 +594,19 @@ static int sbs_get_battery_presence_and_health(
 		return ret;
 	}
 
-	if (psp == POWER_SUPPLY_PROP_PRESENT)
+	if (psp == POWER_SUPPLY_PROP_PRESENT) {
 		val->intval = 1; /* battery present */
-	else { /* POWER_SUPPLY_PROP_HEALTH */
+		if (ret == 0) {
+			int voltage, capacity;
+
+			voltage = sbs_read_word_data(
+				client, sbs_data[REG_VOLTAGE].addr);
+			capacity = sbs_read_word_data(
+				client, sbs_data[REG_CAPACITY].addr);
+			if (voltage == 0 && capacity == 0)
+				val->intval = 0;
+		}
+	} else { /* POWER_SUPPLY_PROP_HEALTH */
 		if (sbs_bat_needs_calibration(client)) {
 			val->intval = POWER_SUPPLY_HEALTH_CALIBRATION_REQUIRED;
 		} else {
-- 
2.43.0