Messages in this thread | | | Subject | Re: [PATCH v2 1/2] leds: Add Intel Cherry Trail Whiskey Cove PMIC LEDs | From | Jacek Anaszewski <> | Date | Fri, 15 Feb 2019 23:31:25 +0100 |
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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
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