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[83.28.183.179]) by smtp.gmail.com with ESMTPSA id b20sm1616641lfg.94.2019.02.15.13.43.17 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Feb 2019 13:43:18 -0800 (PST) Subject: Re: [PATCH v2 1/2] leds: Add Intel Cherry Trail Whiskey Cove PMIC LEDs To: Yauhen Kharuzhy , Pavel Machek Cc: Hans de Goede , linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org References: <20190212205901.13037-2-jekhor@gmail.com> <1df39a63-533f-bb68-a056-a0241f148be9@redhat.com> <20190213230731.GA8557@amd> <42078a81-e32e-81b7-528f-d1adb60d31c3@redhat.com> <20190213233806.GA11867@amd> <562e2acd-a60a-2aea-4050-6d9414d23a4e@redhat.com> <20190214111423.GE6132@amd> <92cf09b8-726d-4f1b-94ba-368a66af2246@redhat.com> <2b6faaa5-b21e-a512-de7d-ca21be5045fc@gmail.com> <20190214230307.GA17358@amd> <20190215072709.GD30250@jeknote.loshitsa1.net> From: Jacek Anaszewski Message-ID: Date: Fri, 15 Feb 2019 22:43:17 +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: <20190215072709.GD30250@jeknote.loshitsa1.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Yauhen, On 2/15/19 8:27 AM, Yauhen Kharuzhy wrote: > On Fri, Feb 15, 2019 at 12:03:07AM +0100, Pavel Machek wrote: >> Hi! >> >>>>>> I suggest that we deal with this special case by adding 3 custom >>>>>> sysfs attributes: >>>>>> >>>>>> 1) "mode" which when read, prints, e.g. : >>>>>> manual [on-when-charging] >>>>> >>>>> While this allows _user on console_ to control everything using echo, >>>>> it is not suitable for applications trying to control LEDs. >>>>> >>>>> As there's nothing special about the case here, I believe we should >>>>> have generic solution here. >>>>> >>>>> My preffered solution would be "hardware" trigger that leaves the LED >>>>> in hardware control. >>>> >>>> As you explained in the parts which I snipped, there are many >>>> devices which have a similar choice for a LED being under hw or >>>> user control. I can see how this looks like a trigger and how we >>>> could use the trigger API for this. >>>> >>>> I believe though, that if we implement a "virtual" (for lack of >>>> a better word) trigger for this, that this should be done in the >>>> LED core. I can envision this working like this: >>>> >>>> 1) Add a: >>>> >>>> hw_control_set(struct led_classdev *led_cdev, bool enable_hw_control); >>> >>> Please note that we have support for hw patterns in the pattern trigger. >>> (see how drivers/leds/leds-sc27xx-bltc.c makes use of it for its >>> breathing pattern). >>> We have also support for hw blinking in timer trigger via blink_set op. >>> >>> In addition to that there is brightness_hw_changed sysfs attribute >>> with led_classdev_notify_brightness_hw_changed() LED API. >>> >>> Couldn't they be used in concert to support the specific features >>> of the device in question? >> >> I believe main issue here is this: >> >> Hardware can automatically control the LED according to the charging >> status, or it can be used as normal software-controlled LED. >> >> I believe we should use trigger to select if hardware controls it or >> not (and then add driver-specific files to describe the >> details). Other proposal is in the mail thread, too. > > But there are two kinds of 'hardware control' here in discussion: > 1: > a) PMIC switching LED off/on/breathing/blinking reflected the charging > state (charger is controlled by PMIC entirely without of > software intervention) – 'hw controlled' mode Can we detect when charging is activated? > b) Software controls when LED is on/off/breathing/blinking but > patterns are generated by PMIC – 'sw controlled' mode. > > 2: > a) parameters of lighting (continuous/blinking/breathing) are > set in the PMIC and the PMIC generates patterns > b) blinking/breathing patterns are generated by the software > entirely. > > It seems that we sometimes confuse this two kinds of hw control definitions > in the discussion. > > > The simple use case question: with this hardware and existing LED class > API, what user/app should to do to make LED breathing with hw-generated > pattern? > > As I see, user should activate 'pattern' trigger and write to its hw_pattern attribute... > hm... big pattern which describes every step of breathing? Some > simplified pattern which should be interpreted as 'enable the breathing > an set its frequency' by driver? Which level of simplification will be > suitable? Which criteria of pattern rejection should be? Please see my reply to Hans. We need some simplified device specific syntax of hw_pattern for this device, similarly like in: Documentation/ABI/testing/sysfs-class-led-driver-sc27xx -- Best regards, Jacek Anaszewski