Jacek On 1/8/19 3:18 PM, Jacek Anaszewski wrote: > Hi Dan, > > On 1/7/19 10:14 PM, Dan Murphy wrote: >> Jacek >> >> On 1/7/19 2:59 PM, Jacek Anaszewski wrote: >>> Dan, >>> >>> On 1/7/19 8:36 PM, Dan Murphy wrote: >>>> Jacek >>>> >>>> On 1/7/19 1:13 PM, Jacek Anaszewski wrote: >>>>> On 1/6/19 4:52 PM, Jacek Anaszewski wrote: >>>>>> Hi Pavel, >>>>>> >>>>>> On 1/5/19 11:12 PM, Pavel Machek wrote: >>>>>>> Hi! >>>>>>> >>>>>>>>> Grab yourself an RGB LED and play with it; you'll see what the >>>>>>>>> problems are. It is hard to explain colors over email... >>>>>>>> >>>>>>>> Video [0] gives some overview of lp5024 capabilities. >>>>>>>> >>>>>>>> I don't see any problems in exposing separate red,green,blue >>>>>>>> files and brightness for the devices with hardware support for >>>>>>>> that. >>>>>>> >>>>>>> Well, that's what we do today, as three separate LEDs, right? >>>>>> >>>>>> No. It doesn't allow for setting color intensity by having >>>>>> the color fixed beforehand. Below is relevant excerpt from >>>>>> the lp5024 documentation. This is not something that can be >>>>>> mapped to RGB color space, but rather to HSV/HSL, with the >>>>>> reservation that the hardware implementation uses PWM >>>>>> for setting color intensity. >>>>>> >>>>>> <quote> >>>>>> 8.3.1.2 Independent Intensity Control Per RGB LED Module >>>>>> >>>>>> When color is fixed, the independent intensity-control is used to >>>>>> achieve accurate and flexible dimming control for every RGB LED module. >>>>>> >>>>>> 8.3.1.2.1 Intensity-Control Register Configuration >>>>>> >>>>>> Every three consecutive output channels are assigned to their respective >>>>>> intensity-control register (LEDx_BRIGHTNESS). For example, OUT0, OUT1, >>>>>> and OUT2 are assigned to LED0_BRIGHTNESS, so it is recommended to >>>>>> connect the RGB LEDs in the sequence as shown in Table 1. The LP50xx >>>>>> device allows 256-step intensity control for each RGB LED module, which >>>>>> helps achieve a smooth dimming effect. >>>>>> </quote> >>>>>> >>>>>>> I don't have problem with that, either; other drivers already do >>>>>>> that. He's free to use existing same interface. >>>>>>> >>>>>>> But that is insufficient, as it does not allow simple stuff, such as >>>>>>> turning led "white". >>>>>>> >>>>>>> So... perhaps we should agree on requirements, first, and then we can >>>>>>> discuss solutions? >>>>>>> >>>>>>> Requirements for RGB LED interface: >>>>>>> >>>>>>> 1) Userspace should be able to set the white color >>>>>>> >>>>>>> 2) Userspace should be able to arbitrary color from well known list >>>>>>> and it should approximately match what would CRT, LCD or OLED monitor display >>>>>> >>>>>> The difference is that monitor display driver is pre-calibrated >>>>>> for given display by the manufacturer. With the LED controllers the >>>>>> manufacturer has no control over what LEDs will be connected to the >>>>>> iouts. Therefore it should be not surprising that colors produced >>>>>> by custom LEDs are not as user would expect when comparing to >>>>>> the RGB color displayed on the monitor display. >>>>>> >>>>>> TI provides "Various LED Ring Lighting Patterns Reference Design" [0] >>>>>> that show how to produce various patterns with use of the reference >>>>>> board with LED ring built using sixteen 19-337/R6GHBHC-A01/2T LEDs [1]. >>>>>> >>>>>> Document [0] mentions also specific "Design considerations" in the >>>>>> chapter 2.2: >>>>>> >>>>>> <quote> >>>>>> Several considerations are taken into account for this particular design: >>>>>> • LED map (ring) for meeting the requirement of popular human-machine interaction style. >>>>>> • LED size, numbers and the diffuse design for meeting lighting pattern uniformity. >>>>>> • Analog dimming in the difference ambient light lux without losing dimming resolution in lighting pattern. >>>>>> >>>>>> These considerations apply to most human-machine interaction end equipment with day and night vision >>>>>> designs in some way, but the designer must decide the particular considerations to take into account for a >>>>>> specific design. >>>>>> </quote> >>>>>> >>>>>> This renders your requirement 2) infeasible with use of custom LEDs >>>>>> any fixed algorithm, since the final effect will always heavily depend >>>>> >>>>> Typo here: s/any fixed/and fixed/ >>>>> >>>>>> on the LED circuit design. >>>>>> >>>>>>> >>>>>>> 2a) LEDs probably slightly change color as they age. That's out of >>>>>>> scope, unless the variation is much greater than on monitors. >>>>>>> >>>>>>> 2b) Manufacturing differences cause small color variation. Again, >>>>>>> that's out of scope, unless the variation is much greater than on >>>>>>> monitors. >>>>>>> >>>>>>> Nice to have features: >>>>>>> >>>>>>> 3) Full range of available colors/intensities should be available to >>>>>>> userspace >>>>>>> >>>>>>> 4) Interface should work well with existing triggers >>>>>>> >>>>>>> 5) It would be nice if userland knew how many lumens are produced at >>>>>>> each wavelength for each setting (again, minus aging and manufacturing >>>>>>> variations). >>>>>>> >>>>>>> 6) Complexity of math in kernel should be low, and preferably it >>>>>>> should be integer or fixed point >>>>>>> >>>>>>> Problems: >>>>>>> >>>>>>> a) RGB LEDs are usually not balanced. Setting 100% PWM on >>>>>>> red/green/blue channels will result in nothing close to white >>>>>>> light. In fact, to get white light on N900, blue and green channel's >>>>>>> PWM needs to be set pretty low, as in 5%. >>>>>>> >>>>>>> b) LED class does not define any relation between "brightness" in >>>>>>> sysfs and ammount of light in lumens. Some drivers use close to linear >>>>>>> relation, some use exponential relation. Human eyes percieve logarithm >>>>>>> of lumens. RGB color model uses even more complex function. >>>>>>> >>>>>>> c) Except for white LEDs, LEDs are basically sources of single >>>>>>> wavelength of light, while CRTs and LCDs produce broader >>>>>>> spectrums. >>>>>>> >>>>>>> d) RG, RGBW and probably other LED combinations exist. >>>>>>> >>>>>>> e) Not all "red" LEDs will produce same wavelength. Similar >>>>>>> differences will exist for other colors. >>>>>>> >>>>>>> f) We have existing RGB LEDs represented as three separate >>>>>>> monochromatic LEDs in sysfs. >>>>>> >>>>>> One general question: do you have any solutions in store? >>>>>> >>>>>> [0] http://www.ti.com/lit/ug/tiduee6/tiduee6.pdf >>>>>> [1] http://www.everlight.com/file/ProductFile/19-337-R6GHBHC-A01-2T.pdf >>>>>> >>>>> >>>> >>>> I just wanted to point out that there are 4 total devices right now that use the same mapping >>>> >>>> LP5018, LP5024, LP5030 and the LP5036. >>>> >>>> I can implement what ever we would like to I just need to know what to design against. >>> >>> As you can see from the discussion in this thread it may take some >>> time to work out the interface satisfying everyone. I made some design >>> proposal, but Pavel had no warm word for it. It would be easier if >>> we had more opinions. >> >> I got it from the threads and just the time invested in the FW and HSV. >> >>> >>> How do you feel about using brightness file for setting LEDn_BRIGHTNESS? >> >> I am using that now. The brightness file will adjust the overall brightness of the LED group >> or bank pending on how the LEDs are grouped in the DT file. >> >>> >>> Does increasing LEDn_BRIGHTNESS value (i.e. color intensity) feel like >>> increasing color lightness (i.e. the pattern presented in the video [0] >>> starting from 1:22)? >> >> No unfortunately this is why I introduced the new files to control the individual RGB intensities >> so that the designers can set, tune, create color variations or patterns like the video. >> >> The RGB group brightness would be independent based on lighting conditions, enclosures and diffusers. >> So you could technically be changing color and overall brightness virtually simultaneously > > Oh, so this is surprising. Now it gets even more obscure to me. > > It would be really helpful if we could see a video showing > the LED effects with regard to the applied settings. Well I am doing a test off the command line to ensure the user space can interface with the RGB LED. I can ping someone in product development to see the application of this device if that would help. We did give them a test driver to work on their features but told them the driver is not final until it is in the mainline kernel Dan > >>>> But keep in mind I still need to invest my time in the other TI-lmu patches on my list to complete. >>> >>> Do what you deem most suitable for you. We are here only to help >>> merging the patches, but keeping in mind that kernel interface once >>> introduced must be preserved forever. Therefore we need to do our >>> best to make the best possible design decisions. >>> >>> [0] https://www.youtube.com/watch?v=qdt-alh8i6E >>> >> >> I understand. Maybe I can make the files generic to use for either control or individual control. >> >> We can probably define new ABI's until either HSV or DT frameworks get going. And them make the file presentation >> configurable and default to the new files. > > I am leaning towards it. Just commented on your patches. > -- ------------------ Dan Murphy
