linux-kernel - Re: [PATCH RESEND] LEDS-One-Shot-Timer-Trigger-implementation

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Date:	Tue, 10 Apr 2012 01:21:42 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	NeilBrown <neilb@...e.de>
Cc:	Shuah Khan <shuahkhan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	rpurdie@...ux.intel.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND] LEDS-One-Shot-Timer-Trigger-implementation

On Tue, Apr 10, 2012 at 08:25:06AM +1000, NeilBrown wrote:
> On Sun, 8 Apr 2012 17:06:46 -0700 Dmitry Torokhov <dmitry.torokhov@...il.com>
> wrote:
> 
> > On Mon, Apr 09, 2012 at 09:42:19AM +1000, NeilBrown wrote:
> 
> > > Also, I don't think 'ff' allows for "vibrate for N milliseconds".
> > > It appears that one uses the "rumble" effect and have to say "turn it on",
> > > then "turn it off".  Is that correct?
> > 
> > No, it is not.
> > 
> > > I found 'struct ff_replay' which has a 'length' which is a duration, but it
> > > doesn't seem to be used.
> > 
> > It does, see drivers/input/ff-memless.c where it us used to schedule
> > when effect starts and how long it should play. Non memoryless devices
> > (such as iforce) are supposed to schedule effects themselves.
> > 
> > > 
> > > How would you tell the force feedback framework to play the vibrator for
> > > 120ms, then stop?
> > 
> > By specifying replay->length = 120
> 
> You seem to make a convincing case.  I'll explore this some more and see what
> it is like in practice.
> 
> 
> Clipping from above:
> 
> > 
> > Well, if you consider "input" is really "hid" then FF is really
> > appropriate for iterfacing with a human.
> > 
> 
> A slightly related question.  My phone has accelerometers in it.  I want to
> use them entirely a human-interface-devices.  The device itself can detect
> inversions and taps and jerks and I want to report just those to user-space,
> preferably via the input (aka hid :-) subsystem.  However my understanding is
> that accelerometer drivers aren't welcome as input drivers.  Is that still
> true?
> There is nothing 'industrial' about these accelerometers so I would like to
> avoid 'iio'.  What are your thoughts about this?

I got convinced that 3-axis accelerometers should be included in input
devices, at least until we have a reliable bridge between iio and input.

If you take a look into drivers/input/misc you will find a few of them
there.

Thanks.

-- 
Dmitry
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