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>Parports and their overrides</H1
><P
> The generic <TT
CLASS="LITERAL"
>parport</TT
> sharing code doesn't
directly handle the parallel port hardware. That is done instead
by <SPAN
CLASS="QUOTE"
>"low-level"</SPAN
> <TT
CLASS="LITERAL"
>parport</TT
> drivers.
The function of a low-level <TT
CLASS="LITERAL"
>parport</TT
> driver is
to detect parallel ports, register them with the sharing code, and
provide a list of access functions for each port.
</P
><P
> The most basic access functions that must be provided are ones for
examining the status lines, for setting the control lines, and for
setting the data lines. There are also access functions for
setting the direction of the data lines; normally they are in the
<SPAN
CLASS="QUOTE"
>"forward"</SPAN
> direction (that is, the computer drives
them), but some ports allow switching to <SPAN
CLASS="QUOTE"
>"reverse"</SPAN
>
mode (driven by the peripheral). There is an access function for
examining the data lines once in reverse mode.
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