linux-kernel - Re: Vibrations in input vs. LED was Re: [PATCH v2 0/3] led: ledtrig-transient: add support for hrtimer

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Message-ID: <20171005004045.GD16508@dtor-ws>
Date:   Wed, 4 Oct 2017 17:40:45 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     David Lin <dtwlin@...gle.com>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Pavel Machek <pavel@....cz>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Richard Purdie <rpurdie@...ys.net>,
        Hans de Goede <hdegoede@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh@...nel.org>,
        Rom Lemarchand <romlem@...gle.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>
Subject: Re: Vibrations in input vs. LED was Re: [PATCH v2 0/3] led:
 ledtrig-transient: add support for hrtimer

On Thu, Sep 28, 2017 at 12:22:13PM -0700, David Lin wrote:
> On Wed, Sep 27, 2017 at 10:43 PM, Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
> >>One thing I noticed is that input_ff_create_memless() also does not
> >>use high-resolution timer hence it also does not have the stop-time
> >>precision that I'm looking for.
> >
> > I'll take patches for high resolution timers in ff memless, they should also help with more accurate scheduling of ramping up and fading of events.
> 
> Thanks.
> 
> >
> >>
> >>Another thing is that ff_reply duration value is maxed-out at 32767 ms
> >>(u16) while the Android/userspace requires size long for performing
> >>long notification alert.
> >>
> >
> > You need unattended vibrations lasting longer than 30 seconds? Anyway, replay.length == 0 means endless IIRC, so you only need to schedule stopping. We still will clean up properly if your process crashes or exits or closes the fd.
> 
> Yes, it's up to the application to vibrate for as long as it requires.
> Is there any concern making the duration variable a type long? [If
> this is getting off-topic, I'll follow up with another email]

Yes, given ABI constraints that is not really feasible. I think for
effects longer than 30 seconds you'd have to handle it in the framework
by using replay.length 0 and cancelling the effect some time later.

Thanks.

-- 
Dmitry