linux-kernel - [PATCH] power: supply: ingenic: Fix some error handling paths in ingenic_battery_get

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Date: Sun, 23 Jun 2024 07:50:32 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Paul Cercueil <paul@...pouillou.net>,
	Sebastian Reichel <sre@...nel.org>,
	Artur Rojek <contact@...ur-rojek.eu>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	Sebastian Reichel <sebastian.reichel@...labora.com>,
	linux-mips@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: [PATCH] power: supply: ingenic: Fix some error handling paths in ingenic_battery_get_property()

If iio_read_channel_processed() fails, 'val->intval' is not updated, but it
is still *1000 just after. So, in case of error, the *1000 accumulate and
'val->intval' becomes erroneous.

So instead of rescaling the value after the fact, use the dedicated scaling
API. This way the result is updated only when needed. In case of error, the
previous value is kept, unmodified.

This should also reduce any inaccuracies resulting from the scaling.

Finally, this is also slightly more efficient as it saves a function call
and a multiplication.

Fixes: fb24ccfbe1e0 ("power: supply: add Ingenic JZ47xx battery driver.")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 drivers/power/supply/ingenic-battery.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/power/supply/ingenic-battery.c b/drivers/power/supply/ingenic-battery.c
index 2e7fdfde47ec..0a40f425c277 100644
--- a/drivers/power/supply/ingenic-battery.c
+++ b/drivers/power/supply/ingenic-battery.c
@@ -31,8 +31,9 @@ static int ingenic_battery_get_property(struct power_supply *psy,
 
 	switch (psp) {
 	case POWER_SUPPLY_PROP_HEALTH:
-		ret = iio_read_channel_processed(bat->channel, &val->intval);
-		val->intval *= 1000;
+		ret = iio_read_channel_processed_scale(bat->channel,
+						       &val->intval,
+						       1000);
 		if (val->intval < info->voltage_min_design_uv)
 			val->intval = POWER_SUPPLY_HEALTH_DEAD;
 		else if (val->intval > info->voltage_max_design_uv)
@@ -41,8 +42,9 @@ static int ingenic_battery_get_property(struct power_supply *psy,
 			val->intval = POWER_SUPPLY_HEALTH_GOOD;
 		return ret;
 	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
-		ret = iio_read_channel_processed(bat->channel, &val->intval);
-		val->intval *= 1000;
+		ret = iio_read_channel_processed_scale(bat->channel,
+						       &val->intval,
+						       1000);
 		return ret;
 	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
 		val->intval = info->voltage_min_design_uv;
-- 
2.45.2