linux-kernel - Re: [PATCH] iio: adc: ina2xx: fix missing break statement

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Date:   Wed, 10 Oct 2018 12:42:39 +0200
From:   Stefan Brüns <stefan.bruens@...h-aachen.de>
To:     Colin King <colin.king@...onical.com>
CC:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        <linux-iio@...r.kernel.org>, <kernel-janitors@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: adc: ina2xx: fix missing break statement

On Montag, 8. Oktober 2018 23:09:04 CEST Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> The IIO_CHAN_INFO_SCALE case is missing a break statement and in
> the unlikely event that chan->address is not matched in the nested
> switch statement then the code falls through to the following
> IIO_CHAN_INFO_HARDWAREGAIN case.  Fix this by adding the missing
> break.   While we are fixing this, it's probably a good idea to
> add in a break statement to the IIO_CHAN_INFO_HARDWAREGAIN case
> too (this is a moot point).
> 
> Detected by CoverityScan, CID#1462408 ("Missing break in switch")

Although it is good for code clarity to add a break statement, the code can 
never return anything but -EINVAL in case chan->address is not handled in 
IIO_CHAN_INFO_SCALE:

-----
switch (mask) {
case IIO_CHAN_INFO_SCALE:
   switch (chan->address) {
       case INA2XX_SHUNT_VOLTAGE:
       ... return IIO_VAL_FRACTIONAL;
       
       case INA2XX_BUS_VOLTAGE:
       ... return IIO_VAL_FRACTIONAL;

       case INA2XX_CURRENT:
       ... return IIO_VAL_FRACTIONAL;

       case INA2XX_POWER:
       ... return IIO_VAL_FRACTIONAL;
   }

case IIO_CHAN_INFO_HARDWAREGAIN:
   switch (chan->address) {
       case INA2XX_SHUNT_VOLTAGE:
       ... return IIO_VAL_FRACTIONAL;
       
       case INA2XX_BUS_VOLTAGE:
       ... return IIO_VAL_INT;
   }
}
return -EINVAL;
-----

The addresses handled in INFO_HARDWAREGAIN is a subset of the ones in 
INFO_SCALE.

I would prefer an early "return -EINVAL" here, as it matches better with the 
other "switch (mask)" cases above.

Kind regards,

Stefan

-- 
Stefan Brüns  /  Bergstraße 21  /  52062 Aachen
home: +49 241 53809034     mobile: +49 151 50412019
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