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    SubjectRe: [PATCH RESEND] LEDS-One-Shot-Timer-Trigger-implementation
    On Mon, Apr 09, 2012 at 12:16:05PM -0600, Shuah Khan wrote:
    > On Mon, 2012-04-09 at 10:37 -0700, Dmitry Torokhov wrote:
    > > On Mon, Apr 09, 2012 at 10:55:49AM -0600, Shuah Khan wrote:
    > > > On Sat, 2012-04-07 at 14:56 -0700, Dmitry Torokhov wrote:
    > > > > 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).
    > > > >
    > > >
    > > > Dimitry,
    > > >
    > > > I took a look at these vibra* drivers. The three vibrate drivers are
    > > > chip-set specific. The use-case I have is a non-chip set approach to
    > > > address the use-case when vibrate hardware is not present. Are you
    > > > envisioning a generic approach using ff-memoryless infrastructure?
    > >
    > > Shuah,
    > >
    > > I guess I am confused now. You need some form of hardware to make your
    > > device to vibrate.
    > >
    > > What exactly are you trying to do? Are you trying to:
    > >
    > > 1. activate vibration on devices that can actually do it using LED
    > > interface, or
    > >
    > > 2. use LEDs as an alternative to vibrate on devices that can't
    > > physically vibrate?
    > >
    > > Thanks.
    >
    > What I meant by generic approach is a higher level interface that is not
    > tied too closely to the underlying hardware. Similar to the leds-pwm.c
    > and leds-gpio.c handle gpio and pwm based leds. The vibrate hardware in
    > my sue-case is a gpio based and could pwm based on some phones.

    Ok, so you need to add drivers/input/misc/gpio-vibrate.c and pwm-vibrate.c
    and then use FF to activate them. This way we have all vibrate
    implementation use one subsystem instead of splitting between
    input/led/whatever else people could come up with.

    Thanks.

    --
    Dmitry


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