linux-kernel - Re: [PATCH v7 30/34] i2c: tegra: Clean up variable names

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Date:   Mon, 21 Sep 2020 13:40:59 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 30/34] i2c: tegra: Clean up variable names

On Thu, Sep 17, 2020 at 06:43:28PM +0300, Dmitry Osipenko wrote:
> 17.09.2020 15:21, Thierry Reding пишет:
> > On Wed, Sep 09, 2020 at 01:40:02AM +0300, Dmitry Osipenko wrote:
> >> Rename "ret" variables to "err" in order to make code a bit more
> >> expressive, emphasizing that the returned value is an error code.
> >> Same vice versa, where appropriate.
> >>
> >> Rename variable "reg" to "val" in order to better reflect the actual
> >> usage of the variable in the code and to make naming consistent with
> >> the rest of the code.
> >>
> >> Use briefer names for a few members of the tegra_i2c_dev structure in
> >> order to improve readability of the code.
> >>
> >> All dev/&pdev->dev are replaced with i2c_dev->dev in order to have uniform
> >> code style across the driver.
> >>
> >> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> >> ---
> >>  drivers/i2c/busses/i2c-tegra.c | 173 ++++++++++++++++-----------------
> >>  1 file changed, 86 insertions(+), 87 deletions(-)
> > 
> > That's indeed a nice improvement. One thing did spring out at me,
> > though.
> > 
> >> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> > [...]
> >> @@ -1831,20 +1830,20 @@ static int __maybe_unused tegra_i2c_runtime_suspend(struct device *dev)
> >>  
> >>  	clk_bulk_disable(i2c_dev->nclocks, i2c_dev->clocks);
> >>  
> >> -	return pinctrl_pm_select_idle_state(i2c_dev->dev);
> >> +	return pinctrl_pm_select_idle_state(dev);
> >>  }
> >>  
> >>  static int __maybe_unused tegra_i2c_suspend(struct device *dev)
> >>  {
> >>  	struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev);
> >> -	int err = 0;
> >> +	int ret = 0;
> >>  
> >>  	i2c_mark_adapter_suspended(&i2c_dev->adapter);
> >>  
> >>  	if (!pm_runtime_status_suspended(dev))
> >> -		err = tegra_i2c_runtime_suspend(dev);
> >> +		ret = tegra_i2c_runtime_suspend(dev);
> >>  
> >> -	return err;
> >> +	return ret;
> >>  }
> > 
> > Isn't this exactly the opposite of what the commit message says (and the
> > rest of the patch does)?
> 
> This change makes it to be consistent with the rest of the code. You may
> notice that "Factor out hardware initialization into separate function"
> made a similar change.
> 
> The reason I'm doing this is that the "err" suggests that code returns a
> error failure code, while it could be a success too and you don't know
> for sure by looking only at the part of code. Hence it's cleaner to use
> "err" when error code is returned.

I don't follow that reasoning. Every error code obviously also has a
value for success. Otherwise, what's the point of even having a function
if all it can do is fail. Success has to be an option for code to be any
useful at all, right?

The "err" variable here transports the error code and if that error code
happens to be 0 (meaning success), why does that no longer qualify as an
error code?

Thierry

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