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

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Date:   Fri, 9 Feb 2018 17:03:54 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Greg Kroah-Hartman <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@...r.kernel.org" <linux-input@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] Input: gpio_keys: Add level trigger support for GPIO keys

On Fri, Feb 9, 2018 at 11:23 AM, Baolin Wang <baolin.wang@...aro.org> wrote:
> On 9 February 2018 at 14:39, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
>> On Thu, Feb 8, 2018 at 10:08 PM, Baolin Wang <baolin.wang@...aro.org> wrote:
>>> On some platforms (such as Spreadtrum platform), the GPIO keys can only
>>> be triggered by level type.
>>
>> How do you stop the interrupt from re-triggering as long as the key
>> stays pressed?
>
> We will set the level type irq handler as handle_level_irq(), in this
> function, it will mask and ack the irq firstly.

Wouldn't be ambiguous?

1. User presses the key ->
  a) we got edge followed by level signaling;
  b) IRQ core masks line, calls handler, ACKs, unmasks;
  c) somewhere here Press Event is sent;
  d) we still have level... We get IRQ fired again? But see 1. It
obviously not the case.
2. User releases the key ->
  ...

So, the main question if I understood Dmitry correctly is the period
in time where IRQ line should be masked on one hand, and on the other
it will guarantee that user didn't release-press cylcle.

-- 
With Best Regards,
Andy Shevchenko