The following notes describe the main differences of STREAMS drivers and modules in DDI 8 compared to previous releases of the DDI (the device driver interface in UnixWare) and the ODDI (the device driver interface in OpenServer). They will be useful if you are writing new STREAMS drivers or modules, or you are porting existing drivers or modules to DDI 8. These notes should be read in conjunction with ``Porting drivers to DDI 8''. If you are porting STREAMS drivers or modules from SCO OpenServer 5, you should also read ``Porting SCO OpenServer 5 STREAMS drivers and modules''.
DDI 8 STREAMS drivers and modules must register themselves with the system by passing a drvinfo(D4) structure to the drv_attach(D3) function which is called from their _load(D2) entry point routine. This structure identifies the type of driver, its entry points, and other driver properties of which the kernel must be aware.
In DDI 8,
structure is made available through the
drv_str member of drvinfo
instead of being a global variable.
drv_str member points to a streamtab
structure for STREAMS drivers and modules.
It must be set to NULL for non-STREAMS
drivers. The D_MOD flag must be set in the
drv_flags member of drvinfo
to distinguish a STREAMS module from a STREAMS driver.
Other flags (D_MP, D_HOT, D_UPF)
may be set depending on the properties of the driver.
manual page for details.
Note that if a kernel module wants to act as both a
STREAMS module and a STREAMS driver,
it must call drv_attach
twice, once with D_MOD set and once without.
Every DDI 8 STREAMS driver or module
requires the following entry point routines:
STREAMS drivers that control some hardware device,
such as a directly connected adapter,
are considered to be hardware drivers.
They must provide a
entry point that is pointed to by the
d_config member of the
STREAMS modules and
STREAMS software drivers (``pseudo'' drivers)
that do not provide a
entry point routine
must set the
of the drvops structure to NULL.
Open redirection (or ``cloning'') in DDI 8 works differently than in the ODDI and in previous versions of the DDI. DDI 8 drivers cannot use the clone driver; they are responsible for performing their own open redirection. There is no longer a CLONEOPEN flag or even an sflag argument to open(D2). A DDI 8 driver's open entry point routine checks if a particular channel number (the ``clone channel'') was requested. Each driver picks its own clone channel number or numbers. See the open(D2) manual page for details of how to implement open redirection.
The following STREAMS functions are new to DDI 8:
|msgscgth(D3str)||Construct a DMA scatter/gather list for a message block.|
|strioccall(D3str)||Invoke a function as the completion of an M_IOCTL operation.|
Returns a value of type |
The third argument, fr_rtnp,
is now of type |
Returns a value of type |
|msgpullup(D3str)||Replaces pullupmsg which can panic multiprocessor (MP) systems.|
|put(D3str)||Provides an MP-safe, DDI-conforming equivalent of a direct call to the put entry point.|
The argument, id, is now of type |
When porting ODDI drivers to DDI, additional changes are required to utilize additional DDI functions that are provided:
members of qinit, the queue initialization
structure, should be set to NULL. The addresses of
the open and close routines
for a STREAMS driver or module are
now picked up from the
See the stroptions(D4str) manual page for details of how the members of this structure and its options differ in various releases of the DDI and ODDI.
See the copyreq(D4str), copyresp(D4str), and iocblk(D4str) manual pages for details of how the members of these structures differ between the DDI and ODDI.