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

On Wed, 15 Jul 2026 10:07:47 +0200, Cosmo Chou <[email protected]> said:
> 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 <[email protected]>
> ---
>  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
>
>

Reviewed-by: Bartosz Golaszewski <[email protected]>