linux-kernel - Re: [PATCH v2 7/9] gpio: mockup: pass the chip label as device property

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Message-ID: <20200928140028.GO3956970@smile.fi.intel.com>
Date:   Mon, 28 Sep 2020 17:00:28 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Linus Walleij <linus.walleij@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Kent Gibson <warthog618@...il.com>,
        linux-gpio <linux-gpio@...r.kernel.org>,
        linux-doc <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/9] gpio: mockup: pass the chip label as device
 property

On Mon, Sep 28, 2020 at 03:13:53PM +0200, Bartosz Golaszewski wrote:
> On Mon, Sep 28, 2020 at 3:00 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> >
> > On Mon, Sep 28, 2020 at 12:41:53PM +0200, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > >
> > > While we do check the "chip-name" property in probe(), we never actually
> > > use it. Let's pass the chip label to the driver using device properties
> > > as we'll want to allow users to define their own once dynamically
> > > created chips are supported.
> > >
> > > The property is renamed to "chip-label" to not cause any confusion with
> > > the actual chip name which is of the form: "gpiochipX".
> > >
> 
> ^^^ here, see below
> 
> > > If the "chip-label" property is missing, let's do what most devices in
> > > drivers/gpio/ do and use dev_name().
> >
> > ...
> >
> > > +             snprintf(chip_label, sizeof(chip_label),
> > > +                      "gpio-mockup-%c", i + 'A');
> > > +             properties[prop++] = PROPERTY_ENTRY_STRING("chip-label",
> > > +                                                        chip_label);
> >
> > You added new property, now count is up to 4. But at the same time
> >
> >         #define GPIO_MOCKUP_MAX_PROP  4
> >
> > how do you avoid overflow?
> >
> 
> I renamed the property, the previous "chip-name" is no longer used. In
> fact it was never used but was accounted for in GPIO_MOCKUP_MAX_PROP.

Either I'm missing something or...

Current code in linux-next has 3 properties to be possible

PROPERTY_ENTRY_U32("gpio-base", base);
PROPERTY_ENTRY_U16("nr-gpios", ngpio);
PROPERTY_ENTRY_BOOL("named-gpio-lines");

You adding here
PROPERTY_ENTRY_STRING("chip-label", chip_label);

Altogether after this patch is 4 which is maximum, but since array is passed by
a solely pointer, the terminator is a must.

-- 
With Best Regards,
Andy Shevchenko