Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20191224120709.18247-1-brgl@bgdev.pl> <20191224120709.18247-3-brgl@bgdev.pl>
In-Reply-To: <20191224120709.18247-3-brgl@bgdev.pl>
From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 20 Jan 2020 09:44:43 +0100
Message-ID: <CAMuHMdWigj9_CDdDD49qU-y7r+he53v1NEKE9_0RBQCFUrY-Qw@mail.gmail.com>
Subject: Re: [PATCH v4 02/13] gpiolib: have a single place of calling set_config()
To:     Bartosz Golaszewski <brgl@bgdev.pl>
Cc:     Kent Gibson <warthog618@gmail.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Bartosz,

On Tue, Dec 24, 2019 at 1:08 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>
> Instead of calling the gpiochip's set_config() callback directly and
> checking its existence every time - just add a new routine that performs
> this check internally. Call it in gpio_set_config() and
> gpiod_set_transitory(). Also call it in gpiod_set_debounce() and drop
> the check for chip->set() as it's irrelevant to this config option.
>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -3042,6 +3042,15 @@ EXPORT_SYMBOL_GPL(gpiochip_free_own_desc);
>   * rely on gpio_request() having been called beforehand.
>   */
>
> +static int gpio_do_set_config(struct gpio_chip *gc, unsigned int offset,
> +                             enum pin_config_param mode)
> +{
> +       if (!gc->set_config)
> +               return -ENOTSUPP;
> +
> +       return gc->set_config(gc, offset, mode);
> +}
> +
>  static int gpio_set_config(struct gpio_chip *gc, unsigned int offset,
>                            enum pin_config_param mode)
>  {
> @@ -3060,7 +3069,7 @@ static int gpio_set_config(struct gpio_chip *gc, unsigned int offset,
>         }
>
>         config = PIN_CONF_PACKED(mode, arg);
> -       return gc->set_config ? gc->set_config(gc, offset, config) : -ENOTSUPP;
> +       return gpio_do_set_config(gc, offset, mode);

These two lines are not equivalent: the new code no longer uses the
packed value of mode and arg!
Hence this leads to subsequent cleanups in commits e5e42ad224a040f9
("gpiolib: remove set but not used variable 'config'") and d18fddff061d2796
("gpiolib: Remove duplicated function gpio_do_set_config()").

However, what was the purpose of the PIN_CONF_PACKED() translation?
Why is it no longer needed?

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds