linux-kernel - Re: [PATCH v2] Input: gpio_keys: Add level trigger support for GPIO keys

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Date:   Thu, 1 Mar 2018 15:41:15 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Greg KH <gregkh@...uxfoundation.org>,
        stephen lu <lumotuwe@...il.com>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        Joseph Lo <josephl@...dia.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Input <linux-input@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2] Input: gpio_keys: Add level trigger support for GPIO keys

On 28 February 2018 at 20:53, Linus Walleij <linus.walleij@...aro.org> wrote:
> On Mon, Feb 26, 2018 at 7:24 AM, Baolin Wang <baolin.wang@...aro.org> wrote:
>> On 21 February 2018 at 19:35, Baolin Wang <baolin.wang@...aro.org> wrote:
>>> On 20 February 2018 at 02:11, Rob Herring <robh@...nel.org> wrote:
>
>>>>> diff --git a/Documentation/devicetree/bindings/input/gpio-keys.txt b/Documentation/devicetree/bindings/input/gpio-keys.txt
>>>>> index a949404..e3104bd 100644
>>>>> --- a/Documentation/devicetree/bindings/input/gpio-keys.txt
>>>>> +++ b/Documentation/devicetree/bindings/input/gpio-keys.txt
>>>>> @@ -29,6 +29,8 @@ Optional subnode-properties:
>>>>>       - linux,can-disable: Boolean, indicates that button is connected
>>>>>         to dedicated (not shared) interrupt which can be disabled to
>>>>>         suppress events from the button.
>>>>> +     - gpio-key,level-trigger: Boolean, indicates that button's interrupt
>>>>> +       type is level trigger. Otherwise it is edge trigger as default.
>>>>
>>>> No. Just use 'interrupts' instead of 'gpios' and specify the trigger
>>>> type. Or put both if you need to read the state.
>>>
>>> Okay, so something as below to get the level type from the
>>> 'interrupts' property.
>>> if (fwnode_property_read_u32(child, "interrupts", &button->level_type))
>>>         button->level_type = IRQ_TYPE_NONE;
>>
>> After more thinking, if we use 'interrupts' to indicate the irq type
>> for this case, we cannot specify the irq number due to the irq number
>> should be get by gpiod_to_irq(). So the device nodes look weird, since
>> we should define the index of the interrupt controller instead of the
>> irq type if the #interrupt_cells is set to 1 according to the
>> interrupt controller documentation. What do you think about this?
>
> I think what you're ultimately seeing is a bad fit between this
> GPIO/irq-controller and the Linux gpio keys driver, it doesn't
> have very much to do with the device tree bindings.
>
> What I think is appropriate is to try to create a new input driver
> in Linux that just takes an interrupt, not a GPIO, and let the
> GPIO chip only act as an irqchip for this.
>
> This avoid the complicated step of converting a GPIO to an
> interrupt in order to use it, when all you really want to
> do is use an interrupt, you don't really care about the
> GPIO here, correct?

Sometimes we should set the GPIO debounce, and read GPIO value to
report the event, so I think we can not remove GPIO.

>
> So we would create
> drivers/input/keyboard/interrupt_keys.c
> however I suspect a bunch of code would need to be shared
> with gpio_keys.c so maybe it is necessary to break out the
> parts of gpio_keys.c into its own helper file.
>
> Or maybe even have the
> pure interrupt handling as part of gpio_keys.c, i.e. if the
> driver can't find any associated GPIO, it goes on to
> check if there is an interrupt assigned to the device node
> and use that directly instead.
>
> Either way, Dmitry must be involved.
>
> Yours,
> Linus Walleij



-- 
Baolin.wang
Best Regards