linux-kernel - Re: [PATCH v3 2/6] iio: light: Add gain-time-scale helpers

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Message-ID: <20230318172941.36e41a79@jic23-huawei>
Date:   Sat, 18 Mar 2023 17:29:41 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Matti Vaittinen <mazziesaccount@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Shreeya Patel <shreeya.patel@...labora.com>,
        Paul Gazzillo <paul@...zz.com>,
        Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        Zhigang Shi <Zhigang.Shi@...eon.com>,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH v3 2/6] iio: light: Add gain-time-scale helpers


> >   
> >>>> +		kfree(gts->avail_all_scales_table);  
> > 
> > ...
> >   
> >>>> +	per_time_gains = kcalloc(gts->num_itime, sizeof(int *), GFP_KERNEL);  
> >>>
> >>> sizeof(type) is error prone in comparison to sizeof(*var).  
> >>
> >> Yes and no. In majority of cases where we see sizeof(*var) - the *var is no
> >> longer a pointer as having pointers to pointers is not _that_ common. When
> >> we see sizeof(type *) - we instantly know it is a size of a pointer and not
> >> a size of some other type.
> >>
> >> So yes, while having sizeof(*var) makes us tolerant to errors caused by
> >> variable type changes - it makes us prone to human reader errors. Also, if
> >> someone changes type of *var from pointer to some other type - then he/she
> >> is likely to in any case need to revise the array alloactions too.
> >>
> >> While I in general agree with you that the sizeof(variable) is better than
> >> sizeof(type) - I see that in cases like this the sizeof(type *) is clearer.  
> > 
> > Still get a fundamental disagreement on this. I would insist, but I'm not
> > a maintainer, so you are lucky :-) if Jonathan will not force you to follow
> > my way.  
> 
> In a code you are maintaining it is good to have it in your way as 
> you're responsible for it. This is also why I insist on having things in 
> a way I can read best for a code I plan to maintain - unless the 
> subsystem maintainers see it hard to maintain for them. So, let's see if 
> Jonathan has strong opinions on this one :)

This is one where I strongly prefer sizeof(*per_time_gains)
because it's easier to review.  I don't care so much if it's easier to
modify as reality is these rarely get modified.

I often just 'fix' these up whilst applying.

Jonathan