Installing and onfiguring SCSI drivers

BTLD considerations for host adapter drivers

SCSI host adapter drivers should use the BTLD conventions. Some general hints and tips for producing a BTLD host adapter driver include:

A SCSI host adapter driver must register itself using Sharegister(D3osdi).
The driver will not have been statically configured into the kernel via mscsi. A driver that is present in the kernel (whether loaded at boot-time or by the Link Kit) but not configured in the mscsi file, is described as being ``non-configured''. The kernel reserves space for three non-configured SCSI host adapter drivers; additional non-configured SCSI host adapter drivers are silently ignored, and do not work. For more information, see bootstring(HW).
The mscsi(F) file is used to reserve the required space and to map a SCSI peripheral driver to a specific controller. For example, the following lines in mscsi would allow a non-configured SCSI host adapter driver to function with a SCSI disk, tape, or CD-ROM:
```
   auto Sdsk 0 0 0 0 0
   auto Stp  0 2 0 0 0
   auto Srom 0 5 0 0 0
```
``auto'' is a special word; the line provides information about possible non-configured SCSI host adapter drivers. It is used to allocate space for, at most, a single non-configured SCSI host adapter driver. There may be several ``auto'' lines, but each line must correspond to a different permitted peripheral driver.
Host adapter drivers, as is the case with all drivers, are given a handler prefix which is stored in column 4 of the mdevice file. You should not create a SCSI host adapter driver with a handler prefix of ``auto'', because it would conflict with the ``auto'' word in the mscsi file.
On SCO OpenServer 5 Release 5, a BTLD SCSI host adapter driver can replace a driver that is already present in the kernel. link(HW) For more information, see ``Boot-time loadable drivers''. To BTLD a replacement SCSI host adapter driver, the following must be true:
- The ``Master'' file entry must match the existing Master file entry exactly.
- The existing driver must be disabled when the kernel is started. The disable keyword allows a host adapter driver to be disabled from the bootstring. The syntax is disable=name, where name is the driver's internal name as defined in column 1 of the mdevice(F) file and printed by printcfg(D3oddi). For example,
```
fd(64)unix root=hd(40) swap=hd(41) disable=hf
```
  boots from the floppy device, disabling the hf SCSI host adapter driver.