By Andréss Trapanotto <mail@andrestrapanotto.com.ar>:

And then, the explanation of how it works:

Up to now, LCDd access right to the parallel port thru io functions
(port_in, port_out, etc...). This way needs root permission and the
known of the parallel port io configuration... And this functions are
included in-line from port.h to the driver.

I've written another set some functions (pp_init, pp_bye,
pp_write_data, etc.) in port.c that are not in-line compiled, has a new
struct pp_driver as argument allowing to pass them more parameters (now
we need to tell which port, register and data we want to use, read or
write).

And there is something else that is a wrapper to get old functions
(port_in, port_out, etc) supported for such drivers that are not
modified to use new parallel port functions.

So, if you have an LCD attached to your parallel port (like my hd44780)
without keys attached to it, you can apply this patch and just forget
the io access to the parallel port :)

Well, I hope these could be useful to the project. The patch itself has
some in-line comments but ask me for any doubt.

Best regards, Andrés!