linux-kernel - Re: [PATCH 2/3] auxdisplay: ht16k33: rework input device initialization

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Message-ID: <20170209181018.GB8862@dtor-ws>
Date:   Thu, 9 Feb 2017 10:10:18 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Robin van der Gracht <robin@...tonic.nl>
Cc:     Miguel Ojeda Sandonis <miguel.ojeda.sandonis@...il.com>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH 2/3] auxdisplay: ht16k33: rework input device
 initialization

Hi Robin,

On Wed, Feb 08, 2017 at 05:48:02PM +0100, Robin van der Gracht wrote:
> On Tue, 31 Jan 2017 12:54:37 -0800
> Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > +
> > +	err = devm_request_threaded_irq(&client->dev, client->irq,
> > +					NULL, ht16k33_keypad_irq_thread,
> > +					IRQF_TRIGGER_RISING | IRQF_ONESHOT,
> > +					DRIVER_NAME, keypad);
> 
> I believe the interrupt trigger should be switched to IRQF_TRIGGER_HIGH
> combined with IRQF_ONESHOT, for this new setup. This is causing a race
> condition.
> 
> In the previous situation a 'key data' read was triggered by
> ht16k33_keypad_start(). This cleared the IRQ and gave a (somewhat racy)
> known state. Now, when the IRQ line is HIGH during probe keyscan
> wont work. 
> 
> Also, when ht16k33_keypad_stop() is run while the irq thread is waiting
> for debounce, the scan will be skipped and irq will never be cleared.
> This also breaks keyscan.


You are absolutely right, I shoudl have changed this to
IRQF_TRIGGER_HIGH. I'll resend updated patch series in a minute.

Thanks.

-- 
Dmitry