On Fri, Feb 15, 2019 at 10:43:17PM +0100, Jacek Anaszewski wrote: > 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? Depends on PMIC and charger configuration. Seems there are no common way working for all configurations exists. > > > 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 Thanks, this approach seems easy to implement. > > -- > Best regards, > Jacek Anaszewski -- Yauhen Kharuzhy
