Macro block_info 

macro_rules! block_info {
    (@info $starts:expr, $per_pol:expr, $name:expr, $summary:expr, $params:ty,
        needs [$($n:ident),* $(,)?], gives [$($g:ident),* $(,)?] $(,)?) => { ... };
    (start $($rest:tt)+) => { ... };
    (per_polarization $($rest:tt)+) => { ... };
    ($($rest:tt)+) => { ... };
}

The documentation of a block (BlockInfo) from its parameters, declared with block_params!, and its ports.

block_info!([start | per_polarization] NAME, SUMMARY, PARAMS, needs [FACT, …], gives [FACT, …])

start marks a block that starts a link (it draws or reads the transmitted signal), per_polarization a block written for one polarisation, applied to each polarisation of a dual-polarisation channel with its own symbols; the facts are variants of Fact. See register for a block of another crate.