Messages in this thread | | | Date | Thu, 31 Mar 2016 10:17:36 +0200 | From | Jacek Anaszewski <> | Subject | Re: [PATCH v5 1/4] leds: core: add generic support for RGB Color LED's |
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Hi Heiner,
On 03/30/2016 03:59 PM, Heiner Kallweit wrote: > On Wed, Mar 30, 2016 at 3:03 PM, Pavel Machek <pavel@ucw.cz> wrote: >> Hi! >> >>>> Ok, so: >>>> >>>> a) Do we want RGB leds to be handled by existing subsystem, or do we >>>> need separate layer on top of that? >>>> >>>> b) Does RGB make sense, or HSV? RGB is quite widely used in graphics, >>>> and it is what hardware implements. (But we'd need to do gamma >>>> correction). >>>> >>>> c) My hardware has "acceleration engine", LED is independend from >>>> CPU. That's rather big deal. Does yours? It seems to be quite common, >>>> at least in cellphones. >>>> >>>> Ideally, I'd like to have "triggers", but different ones. As in: if >>>> charging, do yellow " .xX" pattern. If fully charged, do green steady >>>> light. If message is waiting, do blue " x x" pattern. If none of >>>> above, do slow white blinking. (Plus priorities of events). But that's >>>> quite different from existing support...) >>> >>> Please note that HSV colour scheme allows to neatly project monochrome >>> brightness semantics on the RGB realm. I.e. you can have fixed >>> hue and saturation, and by changing the brightness component a perceived >>> colour intensity can be altered. >> >> I see HSV has some advantages. But we already have LEDs with multiple >> colors, and kernel already handles them: >> >> pavel@duo:~$ ls -1 /sys/class/leds/ >> tpacpi:green:batt >> tpacpi:orange:batt >> >> This is physically 2 leds but hidden under one indicator, so you got >> "off", "green", "orange" and "green+orange". > > That's a good example. As long as you can recognize green+orange as > separate lights/colors > (w/o magnifying glass) I wouldn't call it "a LED with multiple colors" > but "multiple > LED devices". > > In my use case we talk about RGB LEDs like the commonly used 5050 SMD RGB LEDs. > And it's not only about using a handful of discrete colors but about > displaying any arbitrary > color. > So far the kernel exposes the physical RGB LEDs as separate LEDs only > and I can't use > a trigger to e.g. set "magenta with 50% brightness".
I think that we should consult more people before pushing the solution upstream. Would you mind writing a message with an explanation of the issue to linux-api list?
Please keep in mind also the information from the "Attributes" section of Documentation/filesystems/sysfs.txt.
-- Best regards, Jacek Anaszewski
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