linux-kernel - Re: [PATCH] staging: iio: meter: use min() for comparison and assignment

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Message-ID: <41a43f3865f3c86c6c2d1fbf3d82c42b685c7041.camel@perches.com>
Date:   Mon, 07 Nov 2022 07:22:24 -0800
From:   Joe Perches <joe@...ches.com>
To:     Dan Carpenter <error27@...il.com>, Deepak R Varma <drv@...lo.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: iio: meter: use min() for comparison and
 assignment

On Mon, 2022-11-07 at 16:08 +0300, Dan Carpenter wrote:
> On Mon, Nov 07, 2022 at 09:40:00AM +0530, Deepak R Varma wrote:
> > Simplify code by using recommended min helper macro for logical
> > evaluation and value assignment. This issue is identified by
> > coccicheck using the minmax.cocci file.
> > 
> > Signed-off-by: Deepak R Varma <drv@...lo.com>
> > ---
> >  drivers/staging/iio/meter/ade7854-i2c.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/iio/meter/ade7854-i2c.c b/drivers/staging/iio/meter/ade7854-i2c.c
> > index a9a06e8dda51..a6ce7b24cc8f 100644
> > --- a/drivers/staging/iio/meter/ade7854-i2c.c
> > +++ b/drivers/staging/iio/meter/ade7854-i2c.ck
> > @@ -61,7 +61,7 @@ static int ade7854_i2c_write_reg(struct device *dev,
> >  unlock:
> >  	mutex_unlock(&st->buf_lock);
> > 
> > -	return ret < 0 ? ret : 0;
> > +	return min(ret, 0);
> 
> The original code is better.
> 
> If it's a failure return the error code.  If it's not return zero.
> 
> You can only compare apples to apples.  min() makes sense if you're
> talking about two lengths.  But here if ret is negative that's an error
> code.  If it's positive that's the number of bytes.  If the error
> code is less than the number of bytes then return that?  What???  It
> makes no sense.
> 
> In terms of run time, this patch is fine but in terms of reading the
> code using min() makes it less readable.

It's not a runtime question, either should compile to the same object
code.  It's definitely a readabiity and standardization issue.

In this case, IMO it'd be better to use the much more common

	if (ret < 0)
		return ret;

	return 0;