.\"	$OpenBSD: ncr.4,v 1.4 2000/03/27 23:28:23 millert Exp $
.\"
.\" Copyright (c) 1994 James A. Jegers
.\" All rights reserved.
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.Dd March 24, 2000
.Dt NCR 4
.Os
.Sh NAME
.Nm ncr
.Nd NCR 53C8xx SCSI driver
.Sh SYNOPSIS
.Cd "ncr* at pci? dev ? function ?"
.Cd "scsibus* at ncr?"
.Pp
.Cd "option FAILSAFE"
.Cd "option NCR_CDROM_ASYNC"
.Cd "option NCR_IOMAPPED"
.Cd "option NCR_TEKRAM_EEPROM"
.Cd "option NCR_VERBOSE=integer"
.Cd "option SCSI_NCR_DFLT_TAGS=integer"
.Cd "option SCSI_NCR_MAX_SYNC=integer"
.Cd "option SCSI_NCR_MAX_WIDE=integer"
.Cd "option SCSI_NCR_SYMBIOS_COMPAT"
.Cd "option SCSI_NCR_TRUST_BIOS"
.Sh DESCRIPTION
The
.Nm
driver provides support for the NCR (now Symbios) 53C810, 53C815, 53C820,
53C825, 53C860, 53C875, 53C876, 53C885, 53C895, and 53C896
.Tn SCSI
controller chips.
.Pp
The following kernel configuration options are available:
.Bl -ohang
.It Cd option FAILSAFE
Disables tagged command queuing and forces asynchronous transfers for
.Tn CD-ROM
devices.
.It Cd option NCR_CDROM_ASYNC
Always use asynchronous transfers with
.Tn CD-ROM
devices.
By default, synchronous transfers are used if the
.Tn CD-ROM
supports it.
.It Cd option NCR_IOMAPPED
Attempt to access the controller chip via I/O port-mapped I/O, falling back
to memory-mapped I/O if the I/O ports couldn't be mapped.
By default, memory-mapped I/O is tried first.
.It Cd option NCR_TEKRAM_EEPROM
Enables support for reading the configuration
.Tn EEPROM
of the Tekram DC-390 series of
.Tn SCSI
cards.
Enable this only if using a Tekram DC-390 card.
.It Cd option NCR_VERBOSE=integer
Specifies the verbosity of driver messages during a kernel boot.
A value of 1 will provide extra information about the controller's
capabilities and setup.  A value of 2 or greater will print information
about the controller's registers.
.It Cd option SCSI_NCR_DFLT_TAGS=integer
Specifies the maximum number of tags per logical unit.
Unless
.Dv FAILSAFE
is defined, the default value is 4.
A value of 0 will disable tagged command queuing.
.It Cd option SCSI_NCR_MAX_SYNC=integer
Specifies the maximum synchronous transfer frequency to use, in kHz.
A value of 0 means asynchronous transfers only.
The default is 25000 (25MHz), but the actual value used depends on
the type of controller chip and what its maximum transfer rate is.
For controllers supporting fast transfers only, this is 10000 (10MHz).
If wide transfers are supported, the value is 20000 (20MHz).
.It Cd option SCSI_NCR_MAX_WIDE=integer
Specifies the maximum
.Tn SCSI
bus width, with 0 meaning 8 bits and 1 meaning 16 bits.
Defaults to 1 on chips that support wide
.Tn SCSI ,
0 otherwise.
Set this to 0 to disable wide transfers even if both controller
and device support them (e.g. when using a wide controller and wide
drive through a narrow cable).
.It Cd option SCSI_NCR_SYMBIOS_COMPAT
Enables the use of the GPIO register as a disk activity indicator.
Enable this if the activity LED isn't working, but make sure the
card doesn't use GPIO for something else.
Cards known to support this:
ASUS SC875, Diamond FirePort 40, and Symbios SYM8751S.
.It Cd option SCSI_NCR_TRUST_BIOS
Specifies that the driver should use the register configuration set by the
firmware instead of configuring the chip itself.
.El
.Sh BUGS
Some Quantum drives (specifically the Atlas series) return
.Dq queue full
responses when a very small number of tags is used which can confuse
the driver.  With such drives, you can use
.Bd -literal
option  SCSI_NCR_DFLT_TAGS=0

.Ed
in your kernel configuration file to disable tagged command queuing.
.Sh SEE ALSO
.Xr cd 4 ,
.Xr ch 4 ,
.Xr intro 4 ,
.Xr scsi 4 ,
.Xr sd 4 ,
.Xr st 4 ,
.Xr uk 4