linux-kernel - Re: [PATCH v2 0/2] eeprom: at24: write-protect pin support

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Date:   Wed, 20 Dec 2017 16:05:32 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Peter Rosin <peda@...ntia.se>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] eeprom: at24: write-protect pin support

2017-12-20 16:00 GMT+01:00 Andy Shevchenko <andy.shevchenko@...il.com>:
> On Wed, Dec 20, 2017 at 2:41 PM, Bartosz Golaszewski <brgl@...ev.pl> wrote:
>> 2017-12-20 11:21 GMT+01:00 Andy Shevchenko <andy.shevchenko@...il.com>:
>>> On Wed, Dec 20, 2017 at 10:26 AM, Bartosz Golaszewski <brgl@...ev.pl> wrote:
>>>> AT24 EEPROMs have a write-protect pin, which - when pulled high -
>>>> inhibits writes to the upper quadrant of memory (although it has been
>>>> observed that on some chips it disables writing to the entire memory
>>>> range).
>>>>
>>>> On some boards, this pin is connected to a GPIO and pulled high by
>>>> default, which forces the user to manually change its state before
>>>> writing. On linux this means that we either need to hog the line all
>>>> the time, or set the GPIO value before writing from outside of the
>>>> at24 driver.
>>>>
>>>> This series adds support for the write-protect pin split into two
>>>> parts. The first patch extends the relevant binding document, while
>>>> the second modifies the at24 code to pull the write-protect GPIO
>>>> low (if present) during write operations.
>>>>
>>>
>>> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
>>>
>>> A one totally minor nit: if it possible now to have one line where
>>> devm_gpiod_get_optional() is called?
>>> You may ignore this nit anyway.
>>>
>>
>> Hi Andy,
>>
>> I'm afraid I don't understand what you mean here. I do use
>> devm_gpiod_get_optional() in patch 2/2.
>
> I meant to do something like
> ...->wp_gpio = devm_gpiod_get_optional(...);
> if (IS_ERR(...))
>   return ...;
>
> So, note that the first is occupied only one line.
>
> --
> With Best Regards,
> Andy Shevchenko

Oh, now I get it.

It doesn't fit into 80 characters if we use &client->dev as the first
argument, but I see that client->dev is used extensively in probe() so
we could probably use a separate struct device *dev helper variable
for that. I'll note it for future refactoring that will happen soon. I
prefer that this patch stays as it is though.

Thanks,
Bartosz