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[83.31.3.73]) by smtp.gmail.com with ESMTPSA id g12-v6sm2764260lja.74.2019.02.17.04.40.11 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 17 Feb 2019 04:40:12 -0800 (PST) Subject: Re: [PATCH v2 1/2] leds: Add Intel Cherry Trail Whiskey Cove PMIC LEDs To: Hans de Goede , Pavel Machek Cc: Yauhen Kharuzhy , linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org References: <92cf09b8-726d-4f1b-94ba-368a66af2246@redhat.com> <2b6faaa5-b21e-a512-de7d-ca21be5045fc@gmail.com> <20190214230307.GA17358@amd> <2a5e2002-e5f1-6da3-8a43-317801b69657@redhat.com> <3d5407a7-9458-f071-a1d5-511b09678e20@gmail.com> <87a21c4e-8e5e-c180-2ff3-eb8170746e71@redhat.com> <80971bc3-1193-83ed-913a-12f6217016c8@gmail.com> <8a263266-a41f-c916-e990-02d04de9b5d0@gmail.com> <20190216193727.GA14305@amd> <2d5c6f50-c41f-655c-ab03-0c66aa911a27@gmail.com> From: Jacek Anaszewski Message-ID: <40e5b41d-9c78-443d-e5c0-f267ddb978b9@gmail.com> Date: Sun, 17 Feb 2019 13:40:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 2/16/19 11:03 PM, Hans de Goede wrote: > Hi, > > On 2/16/19 10:54 PM, Jacek Anaszewski wrote: >> On 2/16/19 8:37 PM, Pavel Machek wrote: >>> Hi! >>> >>>>>>>> I think that should work fine, which means that we can use the >>>>>>>> timer and >>>>>>>> pattern trigger support for the blinking and breathing modes. >>>>>>>> >>>>>>>> That still leaves the switching between user and hw-control modes, >>>>>>>> as discussed the hw-controlled mode could be modelled as a new >>>>>>>> "hardware" >>>>>>>> trigger, but then we cannot choose between on/blink/breathing when >>>>>>>> in hw-controlled mode. As Pavel mentioned, that would require some >>>>>>>> sort of composed trigger, where we have both the hardware and >>>>>>>> timer triggers active for example. >>>>>>>> >>>>>>>> I think it might be easier to just allow turning on/off the >>>>>>>> hardware >>>>>>>> control mode through a special "hardware_control" sysfs >>>>>>>> attribute and >>>>>>>> then use the existing timer and pattern triggers for blinking / >>>>>>>> breathing. >>>>>>> >>>>>>> Pattern trigger exposes pattern file by default and hw_pattern if >>>>>>> pattern_set/get ops are provided. Writing them enables software and >>>>>>> hardware pattern respectively. >>>>>> >>>>>> This is not about software vs hardware pattern. >>>>>> >>>>>> There are 2 *orthogonal*, separate problems/challenges with this >>>>>> LED controller: >>>>>> >>>>>> 1) It has hardware blinking and breathing, as discussed this can be >>>>>> controlled through the timer and pattern triggers, so this problem >>>>>> is solved. >>>>>> >>>>>> 2) It has 2 operating modes: >>>>>> >>>>>> a) Automatic/hardware controlled, in this mode the LED is turned >>>>>> off or on (where on can be continues on, blinking or breathing) >>>>>> by the hardware itself, when in this mode we / userspace is not >>>>>> in control of the LED >>>>>> >>>>>> b) Manual/user controlled mode, in this mode we / userspace can >>>>>> control of the LED. >>>>>> >>>>>> Currently there is no API in the ledclass to switch a LED from >>>>>> automatic controlled to user controlled and back, This is what >>>>>> the proposed hardware trigger was for, to switch to automatic >>>>>> mode. A problem with this is that we still want to be able >>>>>> to chose between continues on, blinking or breathing (when on), >>>>>> configure the max brightness, etc. >>>>> >>>>> Yes, we do have the API to switch a LED from automatic (hardware >>>>> accelerated) control to software control and back. This is pattern >>>>> trigger, which exposes two files for setting pattern: pattern >>>>> and hw_pattern. Writing pattern file switches the device to software >>>>> control mode and writing hw_pattern switches it to the hardware >>>>> control, >>>>> with the possibility of defining device specific ABI syntax to enable >>>>> particular pattern (blinking, breathing or event permanently on >>>>> in case of this device). >>>> >>>> OK, I see. So we would use the hw_pattern for this and the driver >>>> would implement the pattern_set led_classdev callback. >>>> >>>> The pattern_set callback would then expect 6 brightness/time tuples >>>> with the following meaning for the time part of each tupple >>>> >>>> tupple0: charging blinking_on_time >>>> tupple1: charging blinking_off_time >>>> tupple2: charging breathing_time >>>> tupple3: manual blinking_on_time >>>> tupple4: manual blinking_off_time >>>> tupple5: manual breathing_time >>>> >>>> Where only the times in tupple 0-2; or the times in 3-5 can be >>>> non-zero. Having non zero times for both some charging and some >>>> manual values is not allowed. >>>> >>>> If a breathing time is set, none of the other times may be non >>>> 0. If blinkig_on and blinking_off are used then breathing_time >>>> must be 0. >>>> >>>> When configured to blink then blinking_off must be either 0 >>>> (continuously on); or it must be the same as blinking_on. >>>> >>>> >>>> I believe this will work, does this sound ok to you ? >>> >>> I don't pretend to fully understand it, _but_ hw_pattern should really >>> describe the pattern LED should do, not whether it reacts to charging >>> or not. >> >> This is hardware specific and is supposed to have dedicated ABI >> documentation. There's no reason to introduce new mechanisms when >> existing ones fit. It will still describe a pattern but activated >> on some condition. > > Right, but we can control the condition, so either we need to make > the condition part of the pattern as in my recent proposal with: > > tupple0: charging blinking_on_time > tupple1: charging blinking_off_time > tupple2: charging breathing_time > tupple3: manual blinking_on_time > tupple4: manual blinking_off_time > tupple5: manual breathing_time > > As hw_pattern ABI; or we need to add an extra sysfs file to > set the condition. > > So do you prefer the driver to code the condition into the hw_pattern > (see above); or do you prefer a separate sysfs attribute for the condition? OK, so we'll need to add hardware_controlled file to the LED core. It should be exposed only when supported by the hardware, so we will need the flag in leds.h: #define LED_DEV_CAP_HW_CONTROL BIT(24) -- Best regards, Jacek Anaszewski