[erlang-questions] Linked-in drivers: output and control callbacks

[Joel Reymont]

There are two similar callbacks in the driver entry: output and  
control. The signatures are virtually identical.

My understanding is that Port ! {self(),  {command,  Data}} triggers  
output whereas port_command(Port, Data)  triggers control.

When should control be used?

Are there any reasons to use control at all?

Are there any reasons to prefer output over control or vise versa?

	Thanks, Joel

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