Copy a sample MDI driver and modify it
rather than trying to write
an MDI driver from scratch.
This is usually easier,
and the sample drivers convey style
and illustrate techniques and structure
that are not explicitly documented.
NOTE:
Sample MDI drivers for SVR5 and SCO OpenServer 5
are included in the
ndsample and O5ndsamp packages
which can be installed from
the HDK CD-ROM or downloaded from the
HDK homepage.
Initialization
MDI drivers for SVR5 must call the
mdi_get_unit(D3mdi)
and
mdi_printcfg(D3mdi)
functions.
For DDI 8 drivers,
these functions are called from the CFG_ADD subfunction of the
config(D2mdi)
entry point routine;
for DDI 7 drivers,
these functions are called from the
_load(D2mdi)
entry point routine.
MDI drivers for SCO OpenServer 5 must call the
printcfg(D3oddi)
function from the
init(D2oddi)
entry pont routine.
Other messages
MDI drivers should not generate
unnecessary messages when opening the device
or during device operation.
MDI drivers should report
only one initialization message per driver instance.
For DDI drivers, this message is coded in the
_load(D2mdi)
entry point routine
and is generated using the
mdi_printcfg(D3mdi)
function.
For ODDI drivers on SCO OpenServer 5,
this message is coded in the
init(D2oddi)
entry point routine
and is generated using the
printcfg(D3oddi)
function.