On 1/19/19 10:36 PM, Pavel Machek wrote:
Hi!
First, I think we want to decide if RGB LED should be presented as
3 LEDs or as 1 LED... and what to do with existing RGB leds being
presented as 3 LEDs.
I don't think we want to support both RGB and HSV in the kernel. It is
math, and not a nice one.
Yes, both have advantages and disadvantages, but having _both_ in
kernel has disadvantages of both.
One way I could imagine the interface:
RGB LED presented as one LED.
brightness -- controls brightness of whole RGB module.
What algorithm would be used for mapping brightness levels to RGB values
in case of devices without hardware support for that?
Output power = brightness / max_brightness * pwm_channel[x].
IIUC you mean it as a formula for calculating r,g,b, values?
I.e., on brightness setting we would have to do this calculation for
each of three channels?
Then, it will result in changing hue as well. That's why we're
discussing HSV.
pwm_channels -- "1000 240 300" -- "red part should be full on, green
should be pwm controlled to 240/1000, blue should be 300/1000"
pwm_white -- "1000 500 400" -- tells userspace what to write to PWM
channels to get approximately white color.
This would assume that RGB LEDs are always pwm controlled. That
seems to be true for hardware I seen.
Why pwm in the file names? I don't see any gain and only possible
problems. Many LED controllers use current level and not PWM
for driving LEDs.
I want to make sure userspace understands this has linear relation to
output power. I'd like to avoid mentioning color because there power
output is not linear with "RGB"
s/pwm/color/
s/pwm/power/ would work for me.
Power implies physical units. I'd prefer "intensity".
Besides white also other color presets could be defined in DT.
They should not be neccessary. When userspace knows what is white and
that power is linear with values in power_channels, it should be able
to do colorspace conversion itself.
Have you verified it in practice? Would it allow to convert RGB values
of the color displayed on the monitor to LED RGB class intensities,
allowing to achieve similar color on the LED?
--
Best regards,
Jacek Anaszewski
