linux-kernel - Re: [PATCH 2/2] Input: ili210x

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Message-ID: <CAHCN7x+=_FM32JTEKAb=5pPJNvim88cUFuEXgdGhMG9gdr0Emg@mail.gmail.com>
Date:   Mon, 4 Nov 2019 17:40:28 -0600
From:   Adam Ford <aford173@...il.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Sven Van Asbroeck <thesven73@...il.com>,
        Marek Vasut <marex@...x.de>, linux-input@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] Input: ili210x - add ILI2117 support

On Mon, Nov 4, 2019 at 5:36 PM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> On Mon, Nov 04, 2019 at 05:25:23PM -0600, Adam Ford wrote:
> > On Mon, Nov 4, 2019 at 3:43 PM Sven Van Asbroeck <thesven73@...il.com> wrote:
> > >
> > > Hi Adam,
> > >
> > > On Mon, Nov 4, 2019 at 4:28 PM Adam Ford <aford173@...il.com> wrote:
> > > >
> > > > I am using IRQ_TYPE_EDGE_RISING for the 2117A.  Is that correct?  For
> > > > my touchscreen, the IRQ line is low until a touch is detected, so I
> > > > assume we want to capure on the rising edge.
> > >
> > > That is correct for the 2117A, as far as I know. I am using the same
> > > setting.
> > >
> > > >
> > > > Regarding Dmitry's patch,
> > > > Is it a good idea to use msleep in an IRQ?  It seems like using the
> > > > schedule_delayed_work() call seems like it will get in and get out of
> > > > the ISR faster.
> > > >
> > > > If we use msleep and scan again, isn't it possible to starve other processes?
> > >
> > > I believe using msleep() is ok because this is not a "real" interrupt handler,
> > > but a threaded one. It runs in a regular kernel thread, with its interrupt
> > > turned off (but all other interrupts remain enabled). Its interrupt is
> > > re-enabled automatically after the threaded handler returns.
> > >
> > > See
> > > https://elixir.bootlin.com/linux/latest/source/include/linux/interrupt.h#L50
> > >
> > > > > @@ -268,7 +278,7 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data)
> > > > >                 }
> > > > >
> > > > >                 touch = ili210x_report_events(priv, touchdata);
> > > > > -               keep_polling = touch || chip->continue_polling(touchdata);
> > > > > +               keep_polling = chip->continue_polling(touchdata, touch);
> > > > >                 if (keep_polling)
> > > >
> > > > Why not just check the value of touch instead of invoking the function
> > > > pointer which takes the value of touch in as a parameter?
> > > >
> > >
> > > The value of touch must be checked inside the callback, because
> > > some variants use it to decide if they should poll again, and
> > > some do not, such as the ili211x.
> >
> > That makes sense.
> > >
> > > If I have misinterpreted your suggestion, could you perhaps
> > > express it in C, so I can understand better?
> >
> > You explained it.
> > I'm good.
>
> OK, I refreshed the branch with fixes and a couple of new patches. It is
> on top of 5.3 now. If this works for you guys I will be merging it for
> 5.5.

I will test it tomorrow on a 2117a and reply with results.  I am very
excited to see this integrated.

adam
>
> Thanks.
>
> --
> Dmitry