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CL(7M)									CL(7M)

NAME    [Toc]    [Back]

     cl	- CrayLink Driver

SYNOPSIS    [Toc]    [Back]


DESCRIPTION    [Toc]    [Back]

     The cl module provides a raw device interface to XPC (cross partition
     communication).  These devices take advantage of the XPC rendezvous
     capabilities to allow DMA transfers directly from the source to the
     destination without any intermediate copying if possible.	The DMA
     operation is done using the BTE which supports transfers of multiple
     cache lines on cache line boundaries.  Therefore, in order	to avoid the
     overhead of the cl	driver copying data to an intermediate buffer, the
     source and	destination must be 128	byte aligned.  If the transfer is not
     a multiple	of 128 bytes, only the last part of the	cache line will	be
     copied through an intermediate buffer.

     The cross partition raw devices are located in the	directory
     /hw/xplink/raw/<remote_partition>/<device_number>,	where
     <remote_partition>	is the partition ID to which a device should be
     opened, and the <device_number> specifies which of	the 16 possible
     devices to	open.  These devices appear in the hwgraph(4) the first	time a
     remote partition is discovered (or	activated) as two digit	hexadecimal
     numbers.  They are	never removed.

     Once a cl device is opened	using the open(2) system call (and closed
     using close(2)), the file descriptors may be used to exchanged data with
     the remote	partition using	the read(2), write(2), and select(2) system
     calls.  The devices provide a byte	stream type interface.

     open(2), close(2),	read(2), write(2), or select(2)	will fail for the cl
     devices and return	to the calling process if one or more of the following
     are true

     EIO	 XPC could not be established for the partition	requested.

     ENODEV	 The partition to which	communication is requested no longer

     ENODEV	 The cl	raw device requested does not exist on the remote

									Page 1

CL(7M)									CL(7M)

     EINTR	 A synchronous read or write was interrupted before

     ENOTCONN	 The XPC channel for this raw device has been unexpectedly

     EWOULDBLOCK The call would	have blocked if	the O_NONBLOCK flag had	not
		 been specified	to the open(2) function.

     EBUSY	 The raw device	is currently busy connecting or	disconnecting
		 with the remote partition.

     EAGAIN	 The XPC layer is still	setting	up.

     ENOTSUP	 The partition we are trying to	communicate with does not have
		 support for XPC.

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

     open(2), close(2),	select(2), read(2), write(2), mkpart(1m), hwgraph(4)

									PPPPaaaaggggeeee 2222
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