Changes to SCO OpenServer 5 kernel function set

The SVR5 kernel supports a different set of functions than the SCO OpenServer 5 kernel does. The manual pages for SCO OpenServer 5 functions are included in Section D3oddi manual pages, Section D3osdi manual pages, Section D3str manual pages, and Section D3mdi manual pages for reference. Note that the STREAMS and MDI functions are documented in the same sections as the SVR5 functions, and identified with ODDI pseudo-version numbers for STREAMS functions, and mdi: 1 for MDI functions. See ``ODDI driver interface version for SCO OpenServer 5'' for an explanation of the pseudo-versioning scheme used to document the SCO OpenServer 5 driver interfaces.

The pages for SCO OpenServer 5 functions include information about SVR5 features that provide similar functionality. Some of the major issues are summarized below.

Locks and synchronization

The SVR5 kernel includes a rich set of locks and synchronization variables. For a complete discussion of these, see ``Synchronization variables''. Note the following:

• sleep(D3), wakeup(D3), and timeout(D3) are supported only in DDI versions 6 and earlier and only for single-threaded drivers. DDI 8 drivers must be written to use the multiprocessor-safe locks and synchronization variables.

  • Calls to sleep( ) should be replaced with calls to SV_WAIT(D3) or SV_WAIT_SIG(D3). The synchronization variable must first be allocated.

  • Calls to wakeup( ) should be replaced with calls to SV_BROADCAST(D3) or SV_SIGNAL(D3).

  • Calls to timeout( ) should be replaced with calls to itimeout(D3).

• spl(D3) is supported in all single-threaded ddi: versions, but is usually inadequate to protect a region of critical code. Calls to spl( ) should be replaced with calls to LOCK(D3) or TRYLOCK(D3). The lock must first be allocated. Read/write or sleep locks may be better alternatives in some cases. See ``Critical code section'' and ``Spin locks (DDI)''.

• Most calls to lockb(D3oddi), ilockb(D3oddi), and unlockb(D3oddi) can be replaced by calls to LOCK(D3) and UNLOCK(D3). In some cases, it will be better to use read/write locks, sleep locks, or trylocks instead of the simple mutex locks.

• Multithreaded drivers must be identified in all the following ways:

  • The ``$ddi:'' field in the Master(DSP/4dsp) file must be set to one of the multiprocessing ddi: versions.

  • The ``$interface:'' field in the Master(DSP/4dsp) file must be set to Version 2.

  • For DDI 8 drivers, the D_MP flag must be set in the drvinfo(D4) structure.

Memory allocation

See ``Memory allocation'' for information about the memory allocation facilities on both platforms. Especially note the following:

• The SCO OpenServer 5 sptalloc( ) functions are not supported. Use functions such as kmem_alloc(D3) or kmem_alloc_physreq(D3) instead.

• On SCO OpenServer 5 the kmem_alloc(D3) and kmem_zalloc(D3) functions allocate ISA DMA-able memory (below the 16MB boundary) unless the KM_NO_DMA flag is specified. On SVR5 these functions never allocate contiguous memory; use the kmem_alloc_phys( ) function to allocate contiguous memory. When porting from SVR5 to SCO OpenServer 5 be sure to specify the KM_NO_DMA flag to the kmem_alloc( ) functions to avoid wasting the low ranges of memory.

• On SVR5, rmalloc(D3) and related functions can be used to allocate space from a private space management map, similar to the kernel-level malloc( ) functionality that was available in earlier versions of the UNIX operating system.

Other function call changes

• Both SCO OpenServer 5 and SVR5 drivers should use the cmn_err( ) function for driver messages. If your old SCO OpenServer 5 driver includes calls to printf( ), change them to cmn_err( ) calls.

• The SCO OpenServer 5 calldebug(D3oddi) function is roughly equivalent to the SVR5 call_demon(D3) function. Both temporarily halt the system and call the currently configured kernel debugger when debugging the driver.

  Any debugging calls to cmn_err( ) with the CE_PANIC mode should also be replaced with calls to call_demon(D3) on SVR5 or .LR call_demon D3oddi on SCO OpenServer 5.

• Change all SCO OpenServer 5 suspend(D3oddi) calls to SVR5 drv_usecwait(D3) calls.

TTY drivers

SVR5 does not support the traditional clist-based TTY drivers. Instead, serial drivers should be implemented using the STREAMS interface.

Consequently, the following SCO OpenServer 5 functions are not supported in SVR5: getc(D3oddi), getcb(D3oddi), getcf(D3oddi), putc(D3oddi), putcb(D3oddi), putcf(D3oddi), ldistributed(D3oddi), the tty locking functions documented on the tc_tlock(D3oddi) manual page, and the functions documented on the tty(D3oddi) manual page.