linux-kernel - Re: [PATCH v5] gpio: consumer: new virtual driver

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Date:   Thu, 17 Aug 2023 15:38:50 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Kent Gibson <warthog618@...il.com>,
        Jonathan Corbet <corbet@....net>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v5] gpio: consumer: new virtual driver

On Thu, Aug 17, 2023 at 02:14:04PM +0200, Bartosz Golaszewski wrote:
> On Thu, Aug 17, 2023 at 12:03 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> > On Tue, Aug 15, 2023 at 08:56:50PM +0200, Bartosz Golaszewski wrote:

...

> > > +     struct gpio_consumer_device *dev = lookup->parent;
> > > +
> > > +     guard(mutex)(&dev->lock);
> > > +
> > > +     return sprintf(page, "%s\n", lookup->key);

(1)

...

> > > +static ssize_t
> > > +gpio_consumer_lookup_config_offset_show(struct config_item *item, char *page)
> > > +{
> > > +     struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
> > > +     struct gpio_consumer_device *dev = lookup->parent;
> > > +     unsigned int offset;
> > > +
> > > +     scoped_guard(mutex, &dev->lock)
> > > +             offset = lookup->offset;
> > > +
> > > +     return sprintf(page, "%d\n", offset);
> >
> > Consistently it can be simplified same way
> >
> >         guard(mutex)(&dev->lock);
> >
> >         return sprintf(page, "%d\n", lookup->offset);
> >
> > BUT. Thinking about this more. With guard() we put sprintf() inside the lock,
> > which is suboptimal from runtime point of view. So, I think now that all these
> > should actually use scoped_guard() rather than guard().
> >
> 
> Precisely why I used a scoped guard here. Same elsewhere.

So the 1) has to be amended then.

> > > +}

...

> > > +     enum gpio_lookup_flags flags;
> > > +
> > > +     flags = gpio_consumer_lookup_get_flags(item);
> >
> > This is perfectly one line < 80 characters.
> 
> There's nothing wrong with setting the variable on another line though.

Why do we need 3 LoCs instead of a single one? Do you increase your line
statistics? :-) I really would like to know the rationale behind this.

-- 
With Best Regards,
Andy Shevchenko