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PASS(4)			 BSD 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.

BSD			       October 10, 1998				   BSD

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