led_get_color_name() is a safer alternative to led_colors.

led-class-multicolor.c is the only external user of led_colors and its
removal allows unexporting the array.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20240613-cros_ec-led-v3-2-500b50f41e0f@weissschuh.net
Signed-off-by: Lee Jones <lee@kernel.org>

Add a new led_mc_set_brightness() function for in kernel color/brightness
changing of multi-color LEDs.

led-class-multicolor can be build as a module and led_mc_set_brightness()
will have the builtin callers, so put led_mc_set_brightness() inside
led-core instead, just like how led_set_brightness() is part of the core
and not of the led-class object.

This also adds a new LED_MULTI_COLOR led_classdev flag to allow
led_mc_set_brightness() to verify that it is operating on a multi-color
LED classdev, avoiding casting the passed in LED classdev to a multi-color
LED classdev, when it actually is not a multi-color LED.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://lore.kernel.org/r/20240531114124.45346-5-hdegoede@redhat.com
Signed-off-by: Lee Jones <lee@kernel.org>

Given channel intensity, LED brightness and max LED brightness, the
multicolor LED framework helper led_mc_calc_color_components() computes
the color channel brightness as

    chan_brightness = brightness * chan_intensity / max_brightness

Consider the situation when (brightness, intensity, max_brightness) is
for example (16, 15, 255), then chan_brightness is computed to 0
although the fractional divison would give 0.94, which should be rounded
to 1.

Use DIV_ROUND_CLOSEST here for the division to give more realistic
component computation:

    chan_brightness = DIV_ROUND_CLOSEST(brightness * chan_intensity,
                                        max_brightness)

Fixes: 55d5d3b46b08 ("leds: multicolor: Introduce a multicolor class definition")
Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/20230801124931.8661-1-kabel@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>

Introduce a multicolor class that groups colored LEDs
within a LED node.

The multicolor class groups monochrome LEDs and allows controlling two
aspects of the final combined color: hue and lightness. The former is
controlled via the intensity file and the latter is controlled
via brightness file.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
Acked-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
[squashed leds: multicolor: Fix camel case in documentation in]