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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 1 Mar 2018 13:37:47 +0100
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Subject: Re: [PATCH v4] Input: gpio_keys: Add level trigger support for GPIO keys
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Baolin Wang <baolin.wang@linaro.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stephen lu <lumotuwe@gmail.com>,
        Arvind Yadav <arvind.yadav.cs@gmail.com>,
        Joseph Lo <josephl@nvidia.com>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        Philippe Ombredanne <pombredanne@nexb.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-input <linux-input@vger.kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Mark Brown <broonie@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>
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On Thu, Mar 1, 2018 at 1:09 PM, Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Thu, Mar 1, 2018 at 9:36 AM, Baolin Wang <baolin.wang@linaro.org> wrote:
>> On some platforms (such as Spreadtrum platform), the GPIO keys can only
>> be triggered by level type. So this patch introduces one trigger_type to
>> indicate if the button's interrupt type is level trigger or edge trigger.
>
>>                         button->irq =
>>                                 irq_of_parse_and_map(to_of_node(child), 0);
>
> AFAIU, 0 means NO_IRQ, thus,
>
>> +                       if (button->irq)
>> +                               button->trigger_type =
>> +                                       irq_get_trigger_type(button->irq);
>
> irq_get_trigger_type(NO_IRQ) should return 0.
>
> Therefore, if (button->irq) is redundant.
> Did I miss anything?

"irq_of_parse_and_map(to_of_node(child), 0);" is the first interrupt. A
more common way to express the same thing in modern drivers is
'platform_get_irq(pdev, 0)'.

However, there is one more thing I'm missing: with my suggestion
of emulating edge-triggered interrupts in the irqchip/gpio driver, the
trigger type here should also be 'IRQF_TRIGGER_RISING |
IRQF_TRIGGER_FALLING' in the DT description, so I don't think
we need to change the gpio-keys driver at all, just the gpio driver.

       Arnd