linux-kernel - Re: [PATCH v2] iioc: dac: ltc2664: Fix span variable usage in ltc2664_channel

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Message-ID: <5e4f121f-85a4-489f-8949-a5b02be99d09@wanadoo.fr>
Date: Sat, 5 Oct 2024 21:12:23 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Mohammed Anees <pvmohammedanees2003@...il.com>
Cc: Michael Hennerich <michael.hennerich@...log.com>,
 Kim Seer Paller <kimseer.paller@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>,
 Mohammed Anees <pvmohammedanees2003@...il.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iioc: dac: ltc2664: Fix span variable usage in
 ltc2664_channel_config function

Le 05/10/2024 à 19:07, Mohammed Anees a écrit :
> In the current implementation of the ltc2664_channel_config function,

Hi,

Usually () are added after function name.

	In the current implementation of ltc2664_channel_config()

Same for other function in the text below.

> a variable named span is declared and initialized to 0, intended to
> capture the return value of the ltc2664_set_span function. However,
> the output of ltc2664_set_span is directly assigned to chan->span,
> leaving span unchanged. As a result, when the function later checks
> if (span < 0), this condition will never trigger an error since
> span remains 0, this flaw leads to ineffective error handling. The
> current patch resolves this issue by using the ret variable for

Usually imperative is preferred in patch description. This could be:

	Resolve this issue by using the ret variable for...
(without "The current patch")

> getting the return value, later assigning if successful and also
> effectively removing span variable.
> 
> Signed-off-by: Mohammed Anees <pvmohammedanees2003-Re5JQEeQqe8AvxtiuMwx3w@...lic.gmane.org>
> Fixes: 4cc2fc445d2e4e63ed6bd5d310752d88d365f8e4

Fixes should be before S-o-b.

Fixes should be Fixes: <12 chars of sha1> ("<title line>")
So here: Fixes: 4cc2fc445d2e ("iio: dac: ltc2664: Add driver for LTC2664 
and LTC2672")

I think that running "./scripts/checkpatch.pl" on your patch should warn 
about it.

> ---
> v2:
> - Using the ret variable to store the result from ltc2664_set_span
> ---
>   drivers/iio/dac/ltc2664.c | 18 +++++++++++-------
>   1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/dac/ltc2664.c b/drivers/iio/dac/ltc2664.c
> index 5be5345ac5c8..7dafcba7ece7 100644
> --- a/drivers/iio/dac/ltc2664.c
> +++ b/drivers/iio/dac/ltc2664.c
> @@ -516,7 +516,7 @@ static int ltc2664_channel_config(struct ltc2664_state *st)
>   	const struct ltc2664_chip_info *chip_info = st->chip_info;
>   	struct device *dev = &st->spi->dev;
>   	u32 reg, tmp[2], mspan;
> -	int ret, span = 0;
> +	int ret;
>   
>   	mspan = LTC2664_MSPAN_SOFTSPAN;
>   	ret = device_property_read_u32(dev, "adi,manual-span-operation-config",
> @@ -579,20 +579,24 @@ static int ltc2664_channel_config(struct ltc2664_state *st)
>   		ret = fwnode_property_read_u32_array(child, "output-range-microvolt",
>   						     tmp, ARRAY_SIZE(tmp));
>   		if (!ret && mspan == LTC2664_MSPAN_SOFTSPAN) {
> -			chan->span = ltc2664_set_span(st, tmp[0] / 1000,
> +			ret = ltc2664_set_span(st, tmp[0] / 1000,
>   						      tmp[1] / 1000, reg);

Parameters are not aligned anymore with the opening ( of the previous line.

"./scripts/checkpatch.pl --strict" would also warn about it.

> -			if (span < 0)
> -				return dev_err_probe(dev, span,
> +			if (ret < 0)
> +				return dev_err_probe(dev, ret,
>   						     "Failed to set span\n");
> +			else

No need for 'else'.

> +				chan->span = ret;
>   		}
>   
>   		ret = fwnode_property_read_u32_array(child, "output-range-microamp",
>   						     tmp, ARRAY_SIZE(tmp));
>   		if (!ret) {
> -			chan->span = ltc2664_set_span(st, 0, tmp[1] / 1000, reg);
> -			if (span < 0)
> -				return dev_err_probe(dev, span,
> +			ret = ltc2664_set_span(st, 0, tmp[1] / 1000, reg);
> +			if (ret < 0)
> +				return dev_err_probe(dev, ret,
>   						     "Failed to set span\n");
> +			else

No need for 'else'.

CJ

> +				chan->span = ret;
>   		}
>   	}
>