Messages in this thread | | | Date | Sun, 8 Apr 2012 17:06:46 -0700 | From | Dmitry Torokhov <> | Subject | Re: [PATCH RESEND] LEDS-One-Shot-Timer-Trigger-implementation |
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On Mon, Apr 09, 2012 at 09:42:19AM +1000, NeilBrown wrote: > On Sat, 7 Apr 2012 14:56:41 -0700 Dmitry Torokhov <dmitry.torokhov@gmail.com> > 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). > > > > Thanks. > > > > I don't see that using a "force feedback" "input" device to control a > vibrator - which is neither "force feedback" nor "input", makes any more > sense than using an "led" device to control something that isn't an LED. > So we are even there.
Well, if you consider "input" is really "hid" then FF is really appropriate for iterfacing with a human.
> > I think driving leds by writing to sysfs files is lot easier (for scripting > languages particularly) than the ioctls or binary writes needed for managing > input devices. > > Of course, if the 'input' framework were used for controlling all LEDs - > rather than just the LEDs on keyboard - then it might make sense... > > 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
Thanks.
-- Dmitry
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