[PATCH v3 5/6] leds: aw2013: Prevent writes to unpowered chip

[Paul Sajna]

Replace chip_in_use check with chip->enabled boolean in
aw20xx_brightness_set

During teardown, probe, or unregistration, the LED core initializes
cdev->brightness to 0 and queues a work to set the brightness to 0.
This can also be triggered by unprivileged user space via sysfs by
writing 0 to the brightness file when already 0.

When this occurs, aw2013_chip_in_use() evaluates to false and skips
enabling the regulators:

Because aw2013_chip_enable() is skipped, the driver then unconditionally
calls regmap_write() and regmap_update_bits(), which perform I2C
transactions to the unpowered chip.

To prevent writing gcr=0 when we couldn't power on the chip,
add aw2013_chip_poweroff()

To prevent turning the chip on/off unneccessarily, add a check for
writing brightness to 0.

Signed-off-by: Paul Sajna <sajattack@xxxxxxxxxxxxxxxx>
---
 drivers/leds/leds-aw2013.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/leds/leds-aw2013.c b/drivers/leds/leds-aw2013.c
index 3b2be960c04d..6e661afd7775 100644
--- a/drivers/leds/leds-aw2013.c
+++ b/drivers/leds/leds-aw2013.c
@@ -193,15 +193,13 @@ static int aw2013_chip_init(struct aw2013 *chip)
 	return ret;
 }
 
-static void aw2013_chip_disable(struct aw2013 *chip)
+static void aw2013_chip_poweroff(struct aw2013 *chip)
 {
 	int ret;
 
 	if (!chip->enabled)
 		return;
 
-	regmap_write(chip->regmap, AW2013_GCR, 0);
-
 	ret = regulator_bulk_disable(ARRAY_SIZE(chip->regulators),
 				     chip->regulators);
 	if (ret) {
@@ -213,6 +211,16 @@ static void aw2013_chip_disable(struct aw2013 *chip)
 	chip->enabled = false;
 }
 
+static void aw2013_chip_disable(struct aw2013 *chip)
+{
+	if (!chip->enabled)
+		return;
+
+	regmap_write(chip->regmap, AW2013_GCR, 0);
+
+	aw2013_chip_poweroff(chip);
+}
+
 static int aw2013_chip_enable(struct aw2013 *chip)
 {
 	int ret;
@@ -231,7 +239,7 @@ static int aw2013_chip_enable(struct aw2013 *chip)
 
 	ret = aw2013_chip_init(chip);
 	if (ret)
-		aw2013_chip_disable(chip);
+		aw2013_chip_poweroff(chip);
 
 	return ret;
 }
@@ -253,9 +261,12 @@ static int aw2013_brightness_set(struct led_classdev *cdev,
 	struct aw2013_led *led = container_of(cdev, struct aw2013_led, cdev);
 	int ret, num;
 
+	if (!led->chip->enabled && brightness == 0)
+		return 0;
+
 	mutex_lock(&led->chip->mutex);
 
-	if (aw2013_chip_in_use(led->chip)) {
+	if (!led->chip->enabled) {
 		ret = aw2013_chip_enable(led->chip);
 		if (ret)
 			goto error;
@@ -284,7 +295,12 @@ static int aw2013_brightness_set(struct led_classdev *cdev,
 	if (!aw2013_chip_in_use(led->chip))
 		aw2013_chip_disable(led->chip);
 
+	mutex_unlock(&led->chip->mutex);
+
+	return ret;
+
 error:
+	aw2013_chip_poweroff(led->chip);
 	mutex_unlock(&led->chip->mutex);
 
 	return ret;

-- 
2.55.0