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PASS(4)		       FreeBSD Kernel Interfaces Manual		       PASS(4)

NAME
     pass -- CAM application passthrough driver

SYNOPSIS
     device pass

DESCRIPTION
     The pass driver provides a	way for	userland applications to issue CAM
     CCBs to the kernel.

     Since the pass driver allows direct access	to the CAM subsystem, system
     administrators should exercise caution when granting access to this
     driver.  If used improperly, this driver can allow	userland applications
     to	crash a	machine	or cause data loss.

     The pass driver attaches to every SCSI device found in the	system.	 Since
     it	attaches to every device, it provides a	generic	means of accessing
     SCSI devices, and allows the user to access devices which have no "stan-
     dard" peripheral driver associated	with them.

KERNEL CONFIGURATION
     It	is only	necessary to configure one pass	device in the kernel; pass
     devices are automatically allocated as SCSI devices are found.

IOCTLS
     CAMIOCOMMAND     This ioctl takes most kinds of CAM CCBs and passes them
		      through to the CAM transport layer for action.  Note
		      that some	CCB types are not allowed through the
		      passthrough device, and must be sent through the xpt(4)
		      device instead.  Some examples of	xpt-only CCBs are
		      XPT_SCAN_BUS, XPT_DEV_MATCH, XPT_RESET_BUS,
		      XPT_SCAN_LUN, XPT_ENG_INQ, and XPT_ENG_EXEC.  These CCB
		      types have various attributes that make it illogical or
		      impossible to service them through the passthrough
		      interface.

     CAMGETPASSTHRU   This ioctl takes an XPT_GDEVLIST CCB, and	returns	the
		      passthrough device corresponding to the device in	ques-
		      tion.  Although this ioctl is available through the pass
		      driver, it is of limited use, since the caller must
		      already know that	the device in question is a
		      passthrough device if they are issuing this ioctl.  It
		      is probably more useful to issue this ioctl through the
		      xpt(4) device.

FILES
     /dev/passn	 Character device nodes	for the	pass driver.  There should be
		 one of	these for each device accessed through the CAM subsys-
		 tem.

DIAGNOSTICS
     None.

SEE ALSO
     cam(3), cam(4), cam_cdbparse(3), xpt(4), camcontrol(8)

HISTORY
     The CAM passthrough driver	first appeared in FreeBSD 3.0.

AUTHORS
     Kenneth Merry <ken@FreeBSD.org>

BUGS
     It	might be nice to have a	way to asynchronously send CCBs	through	the
     passthrough driver.  This would probably require some sort	of read/write
     interface or an asynchronous ioctl	interface.

FreeBSD	10.1		       October 10, 1998			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | KERNEL CONFIGURATION | IOCTLS | FILES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | BUGS

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