What is light channel used for?

[GerradLong]

I'm trying to understand what is the light channel: LightsUib uint32_t channels; // 0x000c00ll (ll: light channels, c: caster)

A part of this uint is castShadow info, sure.

But I don't see any examples of
RenderableManager::setLightChannel,
LightManager::setLightChannel or
LightManager::Builder::lightChannel
functions being used.

and the shader code seems to check only with object flag channels to determine if the object should be shaded

void evaluatePunctualLights(const MaterialInputs material,
        const PixelParams pixel, inout vec3 color) {
...

  int channels = object_uniforms_flagsChannels & 0xFF;

    // Iterate point lights
    for ( ; index < end; index++) {
        uint lightIndex = getLightIndex(index);
        Light light = getLight(lightIndex);
        if ((light.channels & channels) == 0) {
            continue;
        }

...

[romainguy]

Light channels can be used to have lights light only certain objects. For instance if you want a key light for a character that should apply only to that character and nothing else in the scene.