From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: Vibrations in input vs. LED was Re: [PATCH v2 0/3] led: ledtrig-transient: add support for hrtimer Date: Wed, 20 Sep 2017 20:44:44 +0200 Message-ID: <4920a403-3cb3-f34e-12f4-909cb1e128bd@gmail.com> References: <20170913175400.42744-1-dtwlin@google.com> <20170913202032.GA30844@amd> <9c75c3a9-4123-c7f3-7725-45ba752d672a@gmail.com> <20170914205804.GA24339@amd> <20170916015809.GA5072@localhost> <9afbd987-b237-24d4-e16a-ddd7fa70766a@gmail.com> <20170917175013.GB13003@amd> <20170920111526.GA3097@amd> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20170920111526.GA3097@amd> Sender: linux-input-owner@vger.kernel.org To: Pavel Machek Cc: linux-input@vger.kernel.org, David Lin , corbet@lwn.net, rpurdie@rpsys.net, hdegoede@redhat.com, gregkh@linuxfoundation.org, robh@kernel.org, romlem@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org List-Id: linux-leds@vger.kernel.org Hi, On 09/20/2017 01:15 PM, Pavel Machek wrote: > On Mon 2017-09-18 22:43:40, Jacek Anaszewski wrote: >> Hi, >> >> On 09/17/2017 07:50 PM, Pavel Machek wrote: >>> Hi! >>> >>>>>> Do you think such an improvement could be harmful in some way, >>>>>> even if it was made optional? >>>>> >>>>> Of course, we can make LED timing accurate down to microseconds. It will >>>>> mean increased overhead -- for "improvement" human can not perceive. >>>>> >>>>> If someone has problems with LED delays not being accurate enough... we >>>>> may want to fix it. But that is not the case here, is it? >>>> >>>> AFAIR David was mentioning that the hr_timer support is perceivable >>> >>> He said that hr_timer support is perceivable _when he is driving >>> vibration motor_. Which he should not do in the first place. >>> >>> Yes, if the difference is perceivable with LED in non-crazy >>> configuration (*), we can take the patch. Is it? Do we have someone >>> not from Google observing it? >>> >>> (*) emulating PWM using blink trigger counts as "crazy" :-) >> >> How about adding CONFIG_LED_TRIGGERS_HR_TIMER_SUPPORT, guarding the >> hr timer support in triggers (timer trigger could also benefit from it) >> with it, and adding "(EXPERIMENTAL)" tag to the config description? > > Why would we want to add code in the LED subsystem that is useless for > LEDs? It could be used for software pwm trigger, there has been at least one an attempt to add such [0]. [0] https://lkml.org/lkml/2015/4/27/493 -- Best regards, Jacek Anaszewski