From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH v2 1/2] leds: Add Intel Cherry Trail Whiskey Cove PMIC LEDs Date: Fri, 15 Feb 2019 23:31:25 +0100 Message-ID: <80971bc3-1193-83ed-913a-12f6217016c8@gmail.com> References: <20190212205901.13037-1-jekhor@gmail.com> <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> <2a5e2002-e5f1-6da3-8a43-317801b69657@redhat.com> <3d5407a7-9458-f071-a1d5-511b09678e20@gmail.com> <87a21c4e-8e5e-c180-2ff3-eb8170746e71@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87a21c4e-8e5e-c180-2ff3-eb8170746e71@redhat.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Hans de Goede , Pavel Machek Cc: Yauhen Kharuzhy , linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org List-Id: linux-leds@vger.kernel.org On 2/15/19 11:26 PM, Hans de Goede wrote: > Hi, > > On 2/15/19 10:42 PM, Jacek Anaszewski wrote: >> Hi all, >> >> On 2/15/19 12:27 PM, Hans de Goede wrote: >>> Hi, >>> >>> On 15-02-19 00:03, 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. >>> >>> Right, so there are really 2 orthogonal issues here: >>> >>> 1) With this hardware the LED is either turned on/off automatically >>> by the PMIC based on charging state; or it is under user control. >>> >>> This is different from the led_classdev_notify_brightness_hw_changed >>> case, where the hardware may update the state underneath the driver, >>> but the driver can still always update the state itself. In this case >>> if the LED is in hw-control mode then the driver cannot turn it on/off. >>> >>> Pavel suggested modeling this with a new "hardware' trigger, where >>> setting the trigger to this trigger will enable the hw-controlled >>> mode and setting any other trigger will switch thing to the >>> user-controlled >>> mode. >> >> We already do have hw_pattern file exposed by pattern trigger. >> It can be used to set hw breathing mode using some device specific >> syntax semantics, documented in dedicated ABI documentation. >> It was introduced for similar case, see >> Documentation/ABI/testing/sysfs-class-led-driver-sc27xx. > > Ah I see, yes that could be used, the pattern would just be a single > integer specifying the cycle time in milliseconds, as nothing > else is configurable. I depends on how the pattern looks like. If it is breathing then we'd need more than one value. > 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. -- Best regards, Jacek Anaszewski