Function render_all 

async fn render_all(
    driver: &mut Driver<SpiTransport<Spi<'static, Async, Master>, Output<'static>, Output<'static>, 2>, 2>,
    state: BacklightState,
) -> Result<(), SpiTransportError<<Spi<'static, Async, Master> as ErrorType>::Error>>

Writes every LED to hardware according to state.

Paints the background white at the current brightness, then overlays the indicator LEDs on top. Called after any state change requiring a full redraw (e.g. thermal-throttle transitions during normal operation).

Errors

Returns Err if any bus transaction fails. See [BacklightDriver::flush].