linux-kernel - Re: [PATCH 3/4] staging: iio: ad7150: simplify i2c SMBus return treatment

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Date:   Sat, 4 May 2019 13:36:43 +0300
From:   Alexandru Ardelean <ardeleanalex@...il.com>
To:     Melissa Wen <melissa.srw@...il.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Stefan Popa <stefan.popa@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Barry Song <21cnbao@...il.com>, linux-iio@...r.kernel.org,
        devel@...verdev.osuosl.org, LKML <linux-kernel@...r.kernel.org>,
        kernel-usp@...glegroups.com
Subject: Re: [PATCH 3/4] staging: iio: ad7150: simplify i2c SMBus return treatment

On Sat, May 4, 2019 at 1:26 AM Melissa Wen <melissa.srw@...il.com> wrote:
>
> Since i2c_smbus_write_byte_data returns no-positive value, this commit
> making the treatment of its return value less verbose.
>
> Signed-off-by: Melissa Wen <melissa.srw@...il.com>
> ---
>  drivers/staging/iio/cdc/ad7150.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/staging/iio/cdc/ad7150.c b/drivers/staging/iio/cdc/ad7150.c
> index 4ba46fb6ac02..3a4572a9e5ec 100644
> --- a/drivers/staging/iio/cdc/ad7150.c
> +++ b/drivers/staging/iio/cdc/ad7150.c
> @@ -201,16 +201,12 @@ static int ad7150_write_event_params(struct iio_dev *indio_dev,
>         ret = i2c_smbus_write_byte_data(chip->client,
>                                         ad7150_addresses[chan][4],
>                                         sens);
> -       if (ret < 0)
> +       if (ret)

For i2c_smbus_write_byte_data(), checking "ret < 0" or non-zero, is the same.
Changing this doesn't have any added value.

>                 return ret;
> -
> -       ret = i2c_smbus_write_byte_data(chip->client,
> +       else
> +               return i2c_smbus_write_byte_data(chip->client,
>                                         ad7150_addresses[chan][5],
>                                         timeout);

The introduction of the "else" branch is a bit noisy.
The code was a bit neater (and readable) before the else branch, and
functionally identical.

Well, when I say neater before, you have to understand, that I (and I
assume that some other people who write drivers) have a slight
fixation for this pattern:

example1:
ret = fn1();

if (ret < 0)  // could also be just "if (ret)"
   return ret;

ret = fn2();
if (ret < 0)  // could also be just "if (ret)"
   return ret;

example1a:
+ret = fn3();
+if (ret < 0)  // could also be just "if (ret)"
+    return ret;


Various higher-level programming languages, will discourage this
pattern in favor of neater patterns.

I personally, have a few arguments in favor of this pattern:
1) it is closer to how the machine code ; so, closer to how a
low-level instruction looks like
2) if (ever) this needs to be patched, the patch could be neat (see
example1a) ; the examle assumes that it's been added via a patch at a
later point in time
3) it keeps indentation level to a minimum ; this also aligns with
kernel-coding guidelines
(https://www.kernel.org/doc/html/v4.10/process/coding-style.html )
    (indentation seems a bit OCD-like when someone points it out at a
review, but it has it's value over time)

> -       if (ret < 0)
> -               return ret;
> -
> -       return 0;
>  }
>
>  static int ad7150_write_event_config(struct iio_dev *indio_dev,
> --
> 2.20.1
>