Re: [PATCH] rtc: pcf85363: Fix phantom device registration on missing hardware

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

On 16/07/2026 20:51:42+0800, Cosmo Chou wrote:
> During probe, pcf85363_load_capacitance() writes the oscillator load
> capacitance configuration to the device. However, if the device is
> not physically present on the bus (returning -ENXIO), the driver
> only emits a warning and continues to execute the probe.
> 
> This results in the successful registration of a phantom RTC device
> via devm_rtc_register_device() and its associated nvmem regions.
> Consequently, userspace may attempt to bind to a non-functional
> /dev/rtc node.
> 
> Propagate the I2C error back to the driver core using dev_err_probe()
> to properly abort the probe and prevent phantom device registration.
> 

No, there is no point in this, simply remove the RTC node from you
device tree.

> Fixes: fd9a6a13949a ("rtc: pcf85363: add support for the quartz-load-femtofarads property")
> Signed-off-by: Cosmo Chou <chou.cosmo@gmail.com>
> ---
>  drivers/rtc/rtc-pcf85363.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-pcf85363.c b/drivers/rtc/rtc-pcf85363.c
> index 540042b9eec8..5612330aff40 100644
> --- a/drivers/rtc/rtc-pcf85363.c
> +++ b/drivers/rtc/rtc-pcf85363.c
> @@ -426,8 +426,8 @@ static int pcf85363_probe(struct i2c_client *client)
>  
>  	err = pcf85363_load_capacitance(pcf85363, client->dev.of_node);
>  	if (err < 0)
> -		dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
> -			 err);
> +		return dev_err_probe(&client->dev, err,
> +				     "failed to set xtal load capacitance\n");
>  
>  	pcf85363->rtc->ops = &rtc_ops;
>  	pcf85363->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
> -- 
> 2.43.0
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com