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

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Message-ID: <20241006152533.329d9b59@jic23-huawei>
Date: Sun, 6 Oct 2024 15:25:33 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Mohammed Anees <pvmohammedanees2003@...il.com>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, Michael
 Hennerich <michael.hennerich@...log.com>, Kim Seer Paller
 <kimseer.paller@...log.com>, Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH v2] iioc: dac: ltc2664: Fix span variable usage in
 ltc2664_channel_config function

On Sat,  5 Oct 2024 22:37:22 +0530
Mohammed Anees <pvmohammedanees2003@...il.com> wrote:

> In the current implementation of the ltc2664_channel_config function,
> 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 
> getting the return value, later assigning if successful and also 
> effectively removing span variable.
> 
> Signed-off-by: Mohammed Anees <pvmohammedanees2003@...il.com>
> Fixes: 4cc2fc445d2e4e63ed6bd5d310752d88d365f8e4
> ---
> 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);
> -			if (span < 0)
> -				return dev_err_probe(dev, span,
> +			if (ret < 0)
> +				return dev_err_probe(dev, ret,
>  						     "Failed to set span\n");
> +			else
else is unnecessary here as we have the standard check and error and return
if set pattern.


> +				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
and here.
> +				chan->span = ret;
>  		}
>  	}
>