wdpi man page on BSDi

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WDPI(4)			    BSD Programmer's Manual		       WDPI(4)

NAME
     wdpi - EIDE ATAPI (SCSI over IDE) driver

SYNOPSIS
     wdpi* at wdc? drive ? flags 0
     tg* at wdpi? target?
     options   ATAPICHG

DESCRIPTION
     This driver acts as a SCSI host adapter for IDE ATAPI devices.  These de-
     vices implement the SCSI protocol over an IDE controller/cable.  It is
     not possible to attach an ATAPI device to an ST-506 controller.  Each AT-
     API device on an IDE controller (cable) will appear as a separate SCSI
     host bus adapter with a single target (0) and a single unit (0).

     Only ATAPI CDROM devices have been tested.	 It is possible that ATAPI
     tapes will work but this configuration has not been tested.

     As a SCSI host bus adapter driver, this driver does not directly export
     any devices to user level.	 The SCSI target driver (tg(4))	 ends up a
     child of wdc(4) and the SCSI disk (sd(4)),	 SCSI tape (st(4)),  and SCSI
     generic (sg(4))  drivers end up beneath the SCSI target driver. ATAPI de-
     vices thus appear as standard SCSI devices at user level.

     ATAPI CD changers (conforming to SFF8020i Rev 2.6) are supported if op-
     tion may be omitted to save around 3Kbytes of kernel memory space.

     The configuration flags parameter is broken up as follows:

     Bit 0 (0x0001)	 When set, causes drives that use interrupt driven
			 command initiation to use polled command initiation.
			 If a given drive becomes ready for command data
			 quickly, this option may result in a performance in-
			 crease.  Setting it will also generally cause an in-
			 crease in system CPU overhead.

     Bit 1 (0x0002)	 When set, prevents the ATAPI CD-changer driver from
			 probing the device to determine if it is a changer.

     Bits 8-15 (0xff00)	 Allow a delay to be inserted between each block data
			 transfer operation.  This is needed to avoid data
			 corruption on some misconfigured/broken hardware.
			 The value of these 8 bits can be 0 (no delay), 0xff
			 (I/O done using inw/outw instead of insw/outsw with
			 no additional delay), or 1 through 254 (delay between
			 each inw/outw in microseconds).  If you see data cor-
			 ruption, first try 0xff in this field then try values
			 from 1 up.  Putting large values in this field will
			 increase system overhead.

     It is possible to specify overrides for the flags parameters with the
     boot program's -dev command.

BOOT PARAMETERS
     The following drive parameter can be configured from boot(8) with the
     -parm command. Typically these commands would be added to boot.default(5)
     though they can be set at the ``Boot:'' prompt.  They can be set for in-
     dividual drives by number, or for all drives not explicitly listed when
     specified for ``wdpi*''.

	   use_dma	If this parameter is specified as  ``yes'', DMA is en-
			abled.

SEE ALSO
     sd(4),  st(4),  wdc(4),  wd(4),  boot(8)

HISTORY
     Written by Eric Varsanyi of BSDI for BSD/OS 2.1.

BSDI BSD/OS		       December 13, 1996			     2
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