Re: [PATCH v2] iioc: dac: ltc2664: Fix span variable usage in ltc2664_channel_config function

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 6 Oct 2024 15:25:33 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Sat,  5 Oct 2024 22:37:22 +0530
> Mohammed Anees <pvmohammedanees2003@gmail.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@gmail.com>
> > Fixes: 4cc2fc445d2e4e63ed6bd5d310752d88d365f8e4
Hmm. I see you had a v3. For some reason that hasn't reached my inbox.
Also note the fixes tag was wrong and you've fixed that.

I've picked up v3 and applied it to the fixes-togreg branch of iio.git
and marked it for stable inclusion.

Thanks,

J
> > ---
> > 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;
> >  		}
> >  	}
> >    
> 
>