linux-kernel - Re: [PATCH v2] iio: adc: ad4170-4: Use ERR_PTR() with %pe to improve error logging

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Message-ID: <fe98c2a2-ec8d-4352-a9fb-6f0e798f7268@baylibre.com>
Date: Thu, 7 Aug 2025 11:02:57 -0500
From: David Lechner <dlechner@...libre.com>
To: Salah Triki <salah.triki@...il.com>, Lars-Peter Clausen
 <lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>,
 Marcelo Schmitt <marcelo.schmitt@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: adc: ad4170-4: Use ERR_PTR() with %pe to improve
 error logging

On 8/7/25 3:05 AM, Salah Triki wrote:
> Use `ERR_PTR(ret)` with `%pe` in `ad4170_read_sample()` to properly display
> symbolic error codes (e.g. `-ENOMEM`) instead of raw integers (e.g. `-12`),
> improving readability and debug clarity.
> 
> Signed-off-by: Salah Triki <salah.triki@...il.com>
> ---
> Changes in v2:
>    - Improve commit title
> 
>  drivers/iio/adc/ad4170-4.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad4170-4.c b/drivers/iio/adc/ad4170-4.c
> index 6cd84d6fb08b..6296b5dc930b 100644
> --- a/drivers/iio/adc/ad4170-4.c
> +++ b/drivers/iio/adc/ad4170-4.c
> @@ -1253,11 +1253,11 @@ static int ad4170_read_sample(struct iio_dev *indio_dev,
>  
>  	ret = __ad4170_read_sample(indio_dev, chan, val);
>  	if (ret) {
> -		dev_err(dev, "failed to read sample: %d\n", ret);
> +		dev_err(dev, "failed to read sample: %pe\n", ERR_PTR(ret));
>  
>  		ret2 = ad4170_set_channel_enable(st, chan->address, false);
>  		if (ret2)
> -			dev_err(dev, "failed to disable channel: %d\n", ret2);
> +			dev_err(dev, "failed to disable channel: %pe\n", ERR_PTR(ret2));
>  
>  		return ret;
>  	}

Interesting, I didn't know we had this format specifier. But I think
this is something we would want to do kernel-wide or not at all to stay
consistent.

And if we are doing this in more places, it would make sense to have a new
format specifier for integer error values instead of casting them to
pointers.