linux-kernel - Re: [PATCH v3] iio: adc: mcp3911: simplify code with guard macro

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Date:   Wed, 6 Dec 2023 18:01:26 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Kent Gustavsson <kent@...oris.se>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] iio: adc: mcp3911: simplify code with guard macro

On Tue, 05 Dec 2023 12:16:33 +0100
Marcus Folkesson <marcus.folkesson@...il.com> wrote:

> Use the guard(mutex) macro for handle mutex lock/unlocks.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>
Hi Marcus,

One follow up issue inline.

> ---
> Changes in v3:
> - Return early in good paths as well
> - Rebase against master
> - Link to v2: https://lore.kernel.org/r/20231127-mcp3911-guard-v2-1-9462630dca1e@gmail.com
> 
> Changes in v2:
> - Return directly instead of goto label
> - Link to v1: https://lore.kernel.org/r/20231125-mcp3911-guard-v1-1-2748d16a3f3f@gmail.com
> ---
>  drivers/iio/adc/mcp3911.c | 47 +++++++++++++++--------------------------------
>  1 file changed, 15 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
> index d864558bc087..f4822ecece89 100644
> --- a/drivers/iio/adc/mcp3911.c
> +++ b/drivers/iio/adc/mcp3911.c
> @@ -7,6 +7,7 @@
>   */
>  #include <linux/bitfield.h>
>  #include <linux/bits.h>
> +#include <linux/cleanup.h>
>  #include <linux/clk.h>
>  #include <linux/delay.h>
>  #include <linux/err.h>
> @@ -318,44 +319,34 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
>  	struct mcp3911 *adc = iio_priv(indio_dev);
>  	int ret = -EINVAL;
>  
> -	mutex_lock(&adc->lock);
> +	guard(mutex)(&adc->lock);
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
>  		ret = mcp3911_read(adc,
>  				   MCP3911_CHANNEL(channel->channel), val, 3);
>  		if (ret)
> -			goto out;
> +			return ret;
>  
>  		*val = sign_extend32(*val, 23);
> -
> -		ret = IIO_VAL_INT;
> +		return IIO_VAL_INT;
>  		break;
Why keep the break? It's unreachable code.
Same for other similar cases.

Jonathan


>