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From:   Bartosz Golaszewski <bgolaszewski@baylibre.com>
Date:   Mon, 6 Jul 2020 13:21:18 +0200
Message-ID: <CAMpxmJUxGq3_R7BRGv68ApeNC+g9PDm_kBd0r=8TjFSyTNxFWg@mail.gmail.com>
Subject: Re: [PATCH v5 1/2] gpio: add GPO driver for PCA9570
To:     Sungbo Eo <mans0n@gorani.run>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Michael Walle <michael@walle.cc>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-gpio <linux-gpio@vger.kernel.org>
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On Sun, Jul 5, 2020 at 3:31 PM Sungbo Eo <mans0n@gorani.run> wrote:
>
> NXP PCA9570 is a 4-bit I2C GPO expander without interrupt functionality.
> Its ports are controlled only by a data byte without register address.
>
> Datasheet: https://www.nxp.com/docs/en/data-sheet/PCA9570.pdf
>
> Signed-off-by: Sungbo Eo <mans0n@gorani.run>
> ---
> v5:
> * amended the commit message
> * removed unnecessary castings
> * added data to of_match_table
>
> v4:
> * removed ->direction_input() and ->direction_output()
>   (Seems unnecessary to me)
> * removed ->set_multiple()
>   (I'm not sure this implementation is really correct)
> * added ->get()
>   (DS says we can read the status from the device)
> * read current status during probe
>
> v3:
> * remove mutex
> * rename buffer to out
> * simplify return statements
> * replace ->probe() to ->probe_new()
> * move ngpio to driver_data
>   (PCA9571 is 8-bit so I thought making ngpio configurable is a good idea)

This driver looks nice now but why did you remove the mutex in v3? I
think when Andy commented on that, he meant not understanding why the
error check is protected, not the i2c operations.

Are you sure you don't need this lock?

Bartosz