Re: [RFC PATCH] pwm: TLC591xx PWM driver

[Andrew Lunn <andrew@lunn.ch>]

> But in the end, it is still PWM in the HW level, and also, the
> brightness isn't linear, or even anything like it. At least on my
> backlight, the visible values range from ~230 to 255.

I suspect the narrow range for you is a property of your hardware. For
my WRT1900ac, 0-32 the LEDs look pretty much like off. Above that, i
get light. Should the LED class layer care about this? Probably
not. It seems like the generic backlight layer should have some method
to reduce the 0-255 down to a couple of dozen useful working points.

> That said, I feel that these frameworks, GPIO, PWM and LED are somewhat
> overlapping. Not really my area of expertise, but I imagine a single
> framework containing all those functionalities could be possible.

Humm, i don't think the frameworks overlap that much. I think it is
the hardware which overlaps. You have a device with an output which
you normally connect an LED to, but you could connect anything to. You
can control this pin using a very restricted PWM like scheme, or you
can have it plain off/on.

With hardware like this, you need to decide which it is most like, and
put that framework at the bottom. Then stack generic X->Y layers on
top to get the rest of the functionality.

    Andrew