linux-kernel - Re: [PATCH 5/7] iio: amplifiers: ad8366: use cleanup.h mutex guard

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Message-ID: <e5b175ae-34d4-47f2-92a4-2788f680da36@kernel.org>
Date: Mon, 19 Jan 2026 15:43:07 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: rodrigo.alencar@...log.com, linux-kernel@...r.kernel.org,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org
Cc: Michael Hennerich <Michael.Hennerich@...log.com>,
 Lars-Peter Clausen <lars@...afoo.de>, Jonathan Cameron <jic23@...nel.org>,
 David Lechner <dlechner@...libre.com>, Andy Shevchenko <andy@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Subject: Re: [PATCH 5/7] iio: amplifiers: ad8366: use cleanup.h mutex guard

On 19/01/2026 15:36, Rodrigo Alencar via B4 Relay wrote:
> From: Rodrigo Alencar <rodrigo.alencar@...log.com>
> 
> Changes related to mutex handling:
> - use guard() from cleanup for mutex locking
> - replace mutex_init() for devm_mutex_init()

Why? We see all this from the diff but I do not see benefits.

> 
> Signed-off-by: Rodrigo Alencar <rodrigo.alencar@...log.com>
> ---
>  drivers/iio/amplifiers/ad8366.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/amplifiers/ad8366.c b/drivers/iio/amplifiers/ad8366.c
> index 160a8ab0c2ee..26856cb4216e 100644
> --- a/drivers/iio/amplifiers/ad8366.c
> +++ b/drivers/iio/amplifiers/ad8366.c
> @@ -17,6 +17,7 @@
>   * Copyright 2012-2026 Analog Devices Inc.
>   */
>  
> +#include <linux/cleanup.h>
>  #include <linux/device.h>
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
> @@ -164,7 +165,8 @@ static int ad8366_read_raw(struct iio_dev *indio_dev,
>  	int ret;
>  	int code, gain = 0;
>  
> -	mutex_lock(&st->lock);
> +	guard(mutex)(&st->lock);
> +
>  	switch (m) {
>  	case IIO_CHAN_INFO_HARDWAREGAIN:
>  		code = st->ch[chan->channel];
> @@ -210,7 +212,6 @@ static int ad8366_read_raw(struct iio_dev *indio_dev,
>  	default:
>  		ret = -EINVAL;
>  	}
> -	mutex_unlock(&st->lock);

This does not simplify code.

>  
>  	return ret;
>  };
> @@ -267,7 +268,8 @@ static int ad8366_write_raw(struct iio_dev *indio_dev,
>  		break;
>  	}
>  
> -	mutex_lock(&st->lock);
> +	guard(mutex)(&st->lock);

Neither this.

> +
>  	switch (mask) {
>  	case IIO_CHAN_INFO_HARDWAREGAIN:
>  		st->ch[chan->channel] = code;
> @@ -276,7 +278,6 @@ static int ad8366_write_raw(struct iio_dev *indio_dev,
>  	default:
>  		ret = -EINVAL;
>  	}
> -	mutex_unlock(&st->lock);
>  
>  	return ret;
>  }
> @@ -336,10 +337,13 @@ static int ad8366_probe(struct spi_device *spi)
>  	}
>  
>  	spi_set_drvdata(spi, indio_dev);
> -	mutex_init(&st->lock);
>  	st->spi = spi;
>  	st->type = spi_get_device_id(spi)->driver_data;
>  
> +	ret = devm_mutex_init(&spi->dev, &st->lock);

And this one actually has impact - missing mutex_destroy...

> +	if (ret)
> +		return ret;
> +
>  	switch (st->type) {
>  	case ID_AD8366:
>  		indio_dev->channels = ad8366_channels;
> 


Best regards,
Krzysztof