[PATCH] leds: pca9532: Fix phantom device registration on missing hardware

[Cosmo Chou]

The initial PWM and PSC register writes in pca9532_configure() do not
check the return values of i2c_smbus_write_byte_data(). If the I2C
device is physically absent from the bus, the write fails with -ENXIO.
However, the driver ignores this error and allows probe() to complete
successfully.

This results in the registration of phantom LED class devices and
gpiochips backed by non-existent hardware. Subsequent GPIO reads from
these phantom chips return bogus values (due to -ENXIO being truncated
to an unsigned char in pca9532_gpio_get_value()), silently corrupting
hardware state tracking in userspace.

Propagate the I2C write failures back to probe() so the driver core
can gracefully abort binding and release devres-managed resources.

Fixes: e14fa82439d3 ("leds: Add pca9532 led driver")
Signed-off-by: Cosmo Chou <chou.cosmo@xxxxxxxxx>
---
 drivers/leds/leds-pca9532.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/leds/leds-pca9532.c b/drivers/leds/leds-pca9532.c
index f3bf59495b68..9606c5b294ed 100644
--- a/drivers/leds/leds-pca9532.c
+++ b/drivers/leds/leds-pca9532.c
@@ -397,10 +397,14 @@ static int pca9532_configure(struct i2c_client *client,
 	for (i = 0; i < 2; i++)	{
 		data->pwm[i] = pdata->pwm[i];
 		data->psc[i] = pdata->psc[i];
-		i2c_smbus_write_byte_data(client, PCA9532_REG_PWM(maxleds, i),
-			data->pwm[i]);
-		i2c_smbus_write_byte_data(client, PCA9532_REG_PSC(maxleds, i),
-			data->psc[i]);
+		err = i2c_smbus_write_byte_data(client, PCA9532_REG_PWM(maxleds, i),
+						data->pwm[i]);
+		if (err < 0)
+			return err;
+		err = i2c_smbus_write_byte_data(client, PCA9532_REG_PSC(maxleds, i),
+						data->psc[i]);
+		if (err < 0)
+			return err;
 	}
 
 	data->hw_blink = true;
-- 
2.43.0