On Mon, 27 Jul 2020 10:45:00 +0200 Pavel Machek <pavel@xxxxxx> wrote: > Hi! > > Multicolor is a bit too abstract. Yes, we can have > Green-Magenta-Ultraviolet LED, but so far all the LEDs we support are > RGB, and not even RGB-White or RGB-Yellow variants emerged. > > Multicolor is not a good fit for RGB LED. It does not really know > about LED color. In particular, there's no way to make LED "white". > > Userspace is interested in knowing "this LED can produce arbitrary > color", which not all multicolor LEDs can. > > Proposal: let's add "rgb" to led_colors in > drivers/leds/led-core.c, add corresponding device tree > defines, and use that, instead of multicolor for RGB LEDs. > > We really need to do that now; "white" stuff can wait. > > RGB LEDs are quite common, and it would be good to be able to turn LED > white and to turn it into any arbitrary color. It is essential that > userspace is able to set arbitrary colors, and it might be good to > have that ability from kernel, too... to allow full-color triggers. > > Best regads, > Pavel I am not against adding RGB if you want to somehow teach the subsystem to mix arbitrary color (either by teaching it color curves or some other way). But I think we shouldn't remove multicolor, and here's the reason why: Most of the time I have seen 2 LEDs per ethernet port, green and yellow, but some ports have 2 Bi-Color LEDs, each consisting of green and yellow. I think most of the time these are 2-terminal LEDs. So basically here we have, instead of a RGB LED, a GY LED (GY for green/yellow). Marvell PHYs support something they call Bi-Color LED Mixing. Normally the LED can be either in ON or OFF state (in terms of LED API max_brightness = 1), but with Bi-Color LED Mixing the 2-terminal GY LED supports max_brightness = 8 for both green and yellow channels. Moreover Marvell PHYs support something called DUAL modes. This basically means that this GY LED can be controlled by hardware in several ways. For example one of these DUAL modes has following behavior: LED[1] LED[0] 1000 noact Off Solid On 1000 act Off Blink 100 noact Solid Mix Solid Mix 100 act Blink Mix Blink Mix 10 noact Solid On Off 10 act Blink Off nolink Off Off So if we want to reasonably add support for this configuration of LEDs and to offer the user to configure these DUAL modes via the trigger API, I think these LEDs should be shown in the system as multicolor LEDs. Marek
