linux-kernel - Re: [PATCH v2] gpio: mockup: Allow probing from device tree

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Message-ID: <CAMRc=Mdjm8tgxF_76T3f6r3TwghLKtrFtUv7ywtX3-nEQzVGtA@mail.gmail.com>
Date:   Tue, 27 Oct 2020 19:12:13 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     Bamvor Jian Zhang <bamv2005@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        kernel@...s.com, devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] gpio: mockup: Allow probing from device tree

On Tue, Oct 27, 2020 at 2:54 PM Vincent Whitchurch
<vincent.whitchurch@...s.com> wrote:
>
> Allow the mockup driver to be probed via the device tree without any
> module parameters, allowing it to be used to configure and test higher
> level drivers like the leds-gpio driver and corresponding userspace
> before actual hardware is available.
>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> ---
> v2: Remove most of the added code, since the latest driver doesn't need it.
>     Drop DT binding document, since Rob Herring was OK with not documenting
>     this:
>     https://lore.kernel.org/linux-devicetree/5baa1ae6.1c69fb81.847f2.3ab1@mx.google.com/
>
>  drivers/gpio/gpio-mockup.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
> index 67ed4f238d43..c93892a6936a 100644
> --- a/drivers/gpio/gpio-mockup.c
> +++ b/drivers/gpio/gpio-mockup.c
> @@ -13,6 +13,7 @@
>  #include <linux/gpio/driver.h>
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
> +#include <linux/of.h>

Please keep the includes ordered alphabetically.

>  #include <linux/irq_sim.h>
>  #include <linux/irqdomain.h>
>  #include <linux/module.h>
> @@ -460,9 +461,18 @@ static int gpio_mockup_probe(struct platform_device *pdev)
>         return 0;
>  }
>
> +#ifdef CONFIG_OF
> +static const struct of_device_id gpio_mockup_of_match[] = {
> +       { .compatible = "gpio-mockup", },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
> +#endif

You don't need this ifdef - of_match_ptr() will evaluate to NULL if
CONFIG_OF is disabled and the compiler will optimize this struct out.

Bartosz

> +
>  static struct platform_driver gpio_mockup_driver = {
>         .driver = {
>                 .name = "gpio-mockup",
> +               .of_match_table = of_match_ptr(gpio_mockup_of_match),
>         },
>         .probe = gpio_mockup_probe,
>  };
> @@ -556,8 +566,7 @@ static int __init gpio_mockup_init(void)
>  {
>         int i, num_chips, err;
>
> -       if ((gpio_mockup_num_ranges < 2) ||
> -           (gpio_mockup_num_ranges % 2) ||
> +       if ((gpio_mockup_num_ranges % 2) ||
>             (gpio_mockup_num_ranges > GPIO_MOCKUP_MAX_RANGES))
>                 return -EINVAL;
>
> --
> 2.28.0
>