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

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Date:	Sat, 7 Apr 2012 14:56:41 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Shuah Khan <shuahkhan@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, neilb@...e.de,
	rpurdie@...ux.intel.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND] LEDS-One-Shot-Timer-Trigger-implementation

Hi Shuah,

On Sat, Apr 07, 2012 at 08:13:44AM -0600, Shuah Khan wrote:
> 
> > > +This feature will help implement vibrate functionality which requires one
> > > +time activation of vibrate mode without a continuous vibrate on/off cycles.
> > 
> > They make vibrating LED? ;)
> > 
> > What's going on here?  You're proposing to repurpose the LEDs code to
> > drive vibration devices?  Or some devices couple a LED with a vibration
> > device?
> 
> I owe you filling in the blanks type explanation. Let me describe the
> use-case I am trying to address first. Vibrater function on phones is
> implemented using PWM pins on SoC or PMIC. When there is no such
> hardware present, a software solution is needed. Currently two drivers
> timed-gpio and timed-output (under staging/android in Linux 3.3)
> together implement the software vibrate feature. The main functionality
> it implements is the one time enables of timer to prevent user space
> crashes leaving the phone in vibrate mode causing the battery to drain.
> leds as it is implemented currently, is not suitable to address this
> use-case as it doesn't support one time enables.

So why do not you use memoryless force feedback framework that other
devices use (see drivers/input/misc/*vibra.c drivers).

Thanks.

-- 
Dmitry
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