Input/output modes and drive strengths.

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Re. GPIO modes:

GPIO_MODE_INPUT - high impedance input
GPIO_MODE_OUTPUT - sources, i.e. active high.
GPIO_MODE_OUTPUT_OD - open drain, i.e active low.

But what about these two, is there a schematic that lets me see how they actually function in bi-directional mode?
GPIO_MODE_INPUT_OUTPUT_OD
GPIO_MODE_INPUT_OUTPUT

Also, the IO_MUX table on the last page specifies the default drive strengths as "2'd2". How is that syntax supposed to be read?

Lastly, can all IO be configured to source 40mA or would that damage the chip?