From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753850AbdEIUof (ORCPT ); Tue, 9 May 2017 16:44:35 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:34039 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750795AbdEIUod (ORCPT ); Tue, 9 May 2017 16:44:33 -0400 Subject: Re: [PATCH 0/3] led: ledtrig-transient: add support for hrtimer To: Pavel Machek , David Lin References: <20170430213701.12297-1-dtwlin@google.com> <20170508210602.GA7260@amd> Cc: corbet@lwn.net, rpurdie@rpsys.net, hdegoede@redhat.com, mark.rutland@arm.com, tony.makkiel@daqri.com, linz@li-pro.net, robh@kernel.org, romlem@google.com, joelaf@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org From: Jacek Anaszewski X-Enigmail-Draft-Status: N1110 Message-ID: Date: Tue, 9 May 2017 22:43:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.5.1 MIME-Version: 1.0 In-Reply-To: <20170508210602.GA7260@amd> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/08/2017 11:06 PM, Pavel Machek wrote: > On Sun 2017-04-30 14:36:58, David Lin wrote: >> Hi, >> >> These patch series add the LED_BRIGHTNESS_FAST flag support for >> ledtrig-transient to use hrtimer so that platforms with high-resolution timer >> support can have better accuracy in the trigger duration timing. The need for >> this support is driven by the fact that Android has removed the timed_ouput [1] >> and is now using led-trigger for handling vibrator control which requires the >> timer to be accurate up to a millisecond. However, this flag support would also >> allow hrtimer to co-exist with the ktimer without causing warning to the >> existing drivers [2]. > > Yes, and objection still stands: You are misusing LED subsystem for > vibration motors. We already have support for haptic feedback in input > subsystem. Regardless of whether it is a misuse or not (ledtrig-transient documentation suggests that it is one of use cases) we have to keep it as it has been around for a long time and it has userspace users [0]. Moreover there seems to be broad consensus about it among kernel people [1]. [0] https://android.googlesource.com/platform%2Fhardware%2Flibhardware/+/61701df363310a5cbd95e3e1638baa9526e42c9b [1] https://patchwork.kernel.org/patch/8664831/ -- Best regards, Jacek Anaszewski