On Mon, Aug 31, 2015 at 11:47:06AM +0300, Kalle Jokiniemi wrote: > Hi, > > On 29.08.2015 03:29, Dmitry Torokhov wrote: > >Hi Kalle, > > > >On Fri, Aug 28, 2015 at 02:56:33PM +0300, Kalle Jokiniemi wrote: > >>Sometimes you need to have tighter control over the ff-memless > >>effects. E.g. when creating short button / VKB press effects, > >>the effect duration is typically <= 40ms, and you want to have > >>a short acceleration period in beginning and fade out the end > >>to avoid "electric tooth brush" effect. With 50ms envelope > >>interval this control is not possible. > >> > >>To allow this control without patching over ff-memless, change the > >>FF_ENVELOPE_INTERVAL macro to a module parameter that can be modified > >>via kernel command line or during runtime from > >>/sys/module/ff_memless/parameters/ff_envelope_interval sysfs file. > > > >How would users know that they need to change this parameter? Could we > >maybe adjust sampling time dynamically, based on the attack length of > >the envelope? > > Well, I'm looking after some parts of the Sailfish OS haptics / > vibrator parts, and consider myself a user. For haptic effects (e.g. > the VKB example above), I know I need as short as I can get to be > able to tune those effects to work best with the Hardware I'm > working with. Then for long alarm vibrations, the interval doesn't > matter that much. But typically I would just set it to the smallest > I can get with HZ setting the kernel has. > > I've been thinking the "user" for this setting more as a system > administrator / OS maintainer / device maker setting. But your idea > could maybe work. Top of my head the downside would be added > complexity, and slight "unpredictability" of the function if the > timing changes dynamically. Would we then again need a user space > setting for the threshold where to start using longer timers? I'd say keep the interval between [5,50] msecs and scale it that you have at least N points for the attack duration. I.e if you decide that you want at least 8 points you do: interval = attack_duration / 8; interval = clamp_val(interval, 5, 50); > > BTW, how would you feel about hr timers instead of jiffy based > timing in ff-memless? That is a bit of a bottle neck for me (I see > some jitter on the first event and typical 100Hz kernel only gives > 10ms control interval). I do not have objections to doing this. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
