Manual page for hardware-assisted data mover interface.
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# $NetBSD: Makefile,v 1.117 2002/07/20 03:58:26 thorpej Exp $
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# $NetBSD: Makefile,v 1.118 2002/08/02 00:41:53 thorpej Exp $
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# Makefile for section 9 (kernel function and variable) manual pages.
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@ -28,6 +28,16 @@ MAN= access.9 altq.9 arc4random.9 arp.9 audio.9 autoconf.9 \
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vattr.9 vfs.9 vfsops.9 vme.9 vnode.9 vnodeops.9 vnsubr.9 \
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usbdi.9 uvm.9 wdc.9 wscons.9 wsdisplay.9 wsfont.9 wskbd.9 wsmouse.9
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MAN+= dmover.9
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MLINKS+=dmover.9 dmover_backend_register.9 \
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dmover.9 dmover_backend_unregister.9 \
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dmover.9 dmover_session_create.9 \
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dmover.9 dmover_session_destroy.9 \
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dmover.9 dmover_request_alloc.9 \
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dmover.9 dmover_request_free.9 \
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dmover.9 dmover_process.9 \
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dmover.9 dmover_done.9
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MLINKS+=arp.9 arp_ifinit.9 arp.9 arpresolve.9 arp.9 arpintr.9
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MLINKS+=access.9 kernacc.9 access.9 useracc.9
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MLINKS+=autoconf.9 config_search.9 \
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@ -0,0 +1,557 @@
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.\" $NetBSD: dmover.9,v 1.1 2002/08/02 00:41:53 thorpej Exp $
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.\"
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.\" Copyright (c) 2002 Wasabi Systems, Inc.
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.\" All rights reserved.
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.\"
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.\" Written by Jason R. Thorpe for Wasabi Systems, Inc.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed for the NetBSD Project by
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.\" Wasabi Systems, Inc.
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.\" 4. The name of Wasabi Systems, Inc. may not be used to endorse
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.\" or promote products derived from this software without specific prior
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.\" written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd July 15, 2002
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.Dt DMOVER 9
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.Os
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.Sh NAME
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.Nm dmover_backend_register ,
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.Nm dmover_backend_unregister ,
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.Nm dmover_session_create ,
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.Nm dmover_session_destroy ,
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.Nm dmover_request_alloc ,
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.Nm dmover_request_free ,
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.Nm dmover_process ,
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.Nm dmover_done
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.Nd hardware-assisted data mover interface
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.Sh SYNOPSIS
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.Fd #include \*[Lt]dev/dmover/dmovervar.h\*[Gt]
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.Pp
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Client interface routines:
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.Pp
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.Ft int
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.Fn "dmover_session_create" "const char *, struct dmover_session **"
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.Ft void
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.Fn "dmover_session_destroy" "struct dmover_session *"
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.Ft "struct dmover_request *"
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.Fn "dmover_request_alloc" "struct dmover_session *" "dmover_buffer *"
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.Ft void
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.Fn "dmover_request_free" "struct dmover_request *"
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.Ft void
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.Fn "dmover_process" "struct dmover_request *"
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.Pp
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Back-end interface routines:
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.Pp
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.Ft void
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.Fn "dmover_backend_register" "struct dmover_backend *"
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.Ft void
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.Fn "dmover_backend_unregister" "struct dmover_backend *"
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.Ft void
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.Fn "dmover_done" "struct dmover_request *"
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.Sh DESCRIPTION
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The
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.Nm dmover
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facility provides an interface to hardware-assisted data movers. This
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can be used to copy data from one location in memory to another, clear
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a region of memory, fill a region of memory with a pattern, and perform
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simple operations on multiple regions of memory, such as an XOR, without
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intervention by the CPU.
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.Pp
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The drivers for hardware-assisted data movers present themselves to
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.Nm dmover
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by registering their capabilities. When a client wishes to use a
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.Nm dmover
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function, it creates a session for that function, which identifies back-ends
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capable of performing that function. The client then enqueues requests
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on that session, which the back-ends process asynchronously. The client
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may choose to block until the request is completed, or may have a call-back
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invoked once the request has been completed.
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.Pp
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When a client creates a session, the
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.Nm dmover
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facility identifies back-ends which are capable of handling the requested
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function. When a request is scheduled for processing, the
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.Nm dmover
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scheduler will indentify the best back-end to process the request from
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the list of candidate back-ends, in an effort to provide load balancing,
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while considering the relative performance of each back-end.
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.Pp
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A
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.Nm dmover
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function always has one output region. A function may have zero or more
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input regions, or may use an immediate value as an input. For functions
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which use input regions, the lenghts of each input region and the output
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region must be the same. All
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.Nm dmover
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functions with the same name will have the same number of and type inputs.
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If a back-end attempts to register a function which violates this invariant,
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behavior is undefined.
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.Pp
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The
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.Nm dmover
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facility supports several types of buffer descriptors. For functions
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which use input regions, each input buffer descriptor and the output buffer
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descriptor must be of the same type. This restriction may be removed in
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a future revision of the interface.
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.Pp
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The
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.Nm dmover
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facility may need to interrupt request processing and restart it.
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Clients of the
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.Nm dmover
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facility should take care to avoid unwanted side-effects should this occur.
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In particular, for functions which use input regions, no input region may
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overlap with the output region.
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.Ss DATA STRUCTURES
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The
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.Nm dmover
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facility shares several data structures between the client and
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back-end in order to describe sessions and requests.
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.Bd -literal -offset indent
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typedef enum {
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DMOVER_BUF_LINEAR,
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DMOVER_BUF_UIO
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} dmover_buffer_type;
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typedef struct {
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void *l_addr;
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size_t l_len;
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} dmover_buf_linear;
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typedef union {
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dmover_buf_linear dmbuf_linear;
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struct uio *dmbuf_uio;
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} dmover_buffer;
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.Ed
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.Pp
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Together, these data types are used to describe buffer data structures
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which the
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.Nm dmover
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facility understands. Additional buffer types may be added in future
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revisions of the
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.Nm dmover
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interface.
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.Pp
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The
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.Fa dmover_assignment
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structure contains the information about the back-end to which a
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request is currently assigned. It contains the following public members:
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.Bl -tag -width "XXXX"
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.It struct dmover_backend *das_backend
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This is a pointer to the back-end.
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.It const struct dmover_algdesc *das_algdesc
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This is a pointer to the algorithm description provided by
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the back-end for the request's function.
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.El
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.Pp
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The
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.Fa dmover_session
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structure contains the following public members:
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.Bl -tag -width "XXXX"
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.It void *dses_cookie
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This is a pointer to client private data.
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.It int dses_ninputs
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This is the number of inputs used by the selected function.
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.El
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.Pp
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The
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.Fa dmover_request
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structure contains the following public members:
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.Bl -tag -width "XXXX"
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.It TAILQ_ENTRY(dmover_request) dreq_dmbq
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Linkage on the back-end's queue of pending requests.
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.It struct dmover_session *dreq_session
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Pointer to the session with which this request is associated. This
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is intended for use by the back-end.
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.It struct dmover_assignment *dreq_assignment
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Pointer to the
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.Fa dmover_assignment
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structure which describes the back-end to which the request is
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currently assigned. The back-end is assigned when the request
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is scheduled with
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.Fn dmover_process .
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.It void (*dreq_callback)(struct dmover_request *)
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This is a pointer to an optional call-back function provided by the
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client. If provided, the call-back is invoked when the request is
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complete. This field must be NULL if
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.Em DMOVER_REQ_WAIT
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is set in
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.Em dreq_flags .
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.It void *dreq_cookie
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This is a pointer to client private data specific to the request.
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.It void *dreq_dmbcookie
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This is a pointer to back-end private data, for use while the back-end
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is actively processing a request.
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.It __volatile int dreq_flags
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The following flags are defined:
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.Bl -tag -width "DMOVER_REQ_RUNNINGXX"
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.It DMOVER_REQ_DONE
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The request has been completed. If not using a call-back, the client
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may poll this bit to determine if a request has been processed.
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.It DMOVER_REQ_ERROR
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An error has occurred while processing the request.
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.It DMOVER_REQ_RUNNING
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The request is currently being executed by the back-end. Once a
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command is running, it cannot be cancelled, and must run to completion.
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.It DMOVER_REQ_WAIT
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If set by the client,
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.Fn dmover_process
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will wait for the request to complete using
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.Xr tsleep 9 .
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This flag may only be used if the caller has a valid thread context.
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If this flag is set, a callback may not be used.
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.El
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.It int dreq_error
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If the
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.Em DMOVER_REQ_ERROR
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bit is set, this contains the
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.Xr errno 2
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value indicating the error that occurred during processing.
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.It dmover_buffer_type dreq_outbuf_type
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The type of the output buffer.
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.It dmover_buffer dreq_outbuf
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The output buffer.
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.It uint8_t dreq_immediate[8]
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This is the input for algorithms which use an immediate value. Values
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smaller than 8 bytes should use the least-significant bytes first. For
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example, a 32-bit integer would occupy bytes 0, 1, 2, and 3.
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.It dmover_buffer_type dreq_inbuf_type
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The type of the input buffer. This is only used if the
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.Nm dmover
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function has one or more inputs.
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.It dmover_buffer *dreq_inbuf
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A pointer to an array of input buffers. This is only used if the
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.Nm dmover
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function has one or more inputs. The number of inputs, and thus the
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number of valid elements in the array, is specified by the algorithm
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description for the session.
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.El
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.Ss CLIENT INTERFACE
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The following functions are provided to the client:
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.Bl -tag -width "XXXX"
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.It int Fn dmover_session_create "const char *function" \
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"struct dmover_session **sessionp"
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.Pp
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The
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.Fn dmover_session_create
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function creates a data mover session for the specified data movement
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function
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.Fa function .
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A handle to the new session is returned in
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.Fa *sessionp .
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.Pp
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The following are valid data movement function names:
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.Bl -tag -width "fill8xx"
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.It Dq zero
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Fill a memory region with zeros. This algorithm has an input count of 0.
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.It Dq fill8
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Fill a memory region with an 8-bit pattern. This algorithm has an input
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count of 0. The pattern is provided in the
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.Em dreq_imm8
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member of the
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.Fa dmover_request
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structure.
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.It Dq copy
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Copy a memory region from one location to another. This algorithm has an
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input count of 1.
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.El
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.Pp
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Users of the
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.Nm dmover
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facility are encouraged to use the following aliases for the well-known
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function names, as doing so saves space and reduces the chance of programming
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errors:
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.Bl -tag -width "DMOVER_FUNC_FILL32xx"
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.It DMOVER_FUNC_ZERO
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.Dq zero
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.Pq Va dmover_funcname_zero
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.It DMOVER_FUNC_FILL8
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.Dq fill8
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.Pq Va dmover_funcname_fill8
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.It DMOVER_FUNC_COPY
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.Dq copy
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.Pq Va dmover_funcname_copy
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.El
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.It void Fn dmover_session_destroy "struct dmover_session *session"
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.Pp
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The
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.Fn dmover_session_destroy
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function tears down a data mover session and releases all resources
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associated with it.
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.It struct dmover_request * Fn dmover_request_alloc \
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"struct dmover_session *session" "dmover_buffer *inbuf"
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.Pp
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The
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.Fn dmover_request_alloc
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function allocates a
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.Nm dmover
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request structure and associates it with the specified session.
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If the
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.Fa inbuf
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argument is non-NULL,
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.Fa inbuf
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is used as the array of input buffer descriptors in the request.
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Otherwise, if
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.Fa inbuf
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is NULL and the
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.Nm dmover
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function requires input buffers, the input buffer descriptors will be
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allocated automatically using
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.Xr malloc 9 .
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.Pp
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If the request structure or input buffer descriptors cannot be allocated,
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.Fn dmover_request_alloc
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return NULL to indicate failure.
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.It void Fn dmover_request_free "struct dmover_request *req"
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.Pp
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The
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.Fn dmover_request_free
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function frees a
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.Nm dmover
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request structure. If the
|
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.Nm dmover
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function requires input buffers, and the input buffer descriptors
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assiciated with
|
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.Fa req
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were allocated by
|
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.Fn dmover_request_alloc ,
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then the input buffer descriptors will also be freed.
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.It void Fn dmover_process "struct dmover_request *req"
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.Pp
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The
|
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.Fn dmover_process
|
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function submits the
|
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.Nm dmover
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request
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.Fa req
|
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for processing. The call-back specified by the request is
|
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invoked when processing is complete.
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.El
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.Pp
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The
|
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.Fn dmover_session_create
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and
|
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.Fn dmover_session_destroy
|
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functions must not be called from interrupt context.
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.Pp
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The
|
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.Fn dmover_request_alloc ,
|
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.Fn dmover_request_free ,
|
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and
|
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.Fn dmover_process
|
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functions may be called from interrupt handlers at levels
|
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.Em IPL_BIO ,
|
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.Em IPL_SOFTCLOCK ,
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and
|
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.Em IPL_SOFTNET ,
|
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or in non-interrupt context.
|
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.Pp
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The request completion call-back is called from a software interrupt
|
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handler at
|
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.Em IPL_SOFTCLOCK .
|
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.Ss BACK-END INTERFACE
|
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A back-end describes the
|
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.Nm dmover
|
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functions it can perform using an array of
|
||||
.Fa dmover_algdesc
|
||||
structures:
|
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.Bd -literal -offset indent
|
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struct dmover_algdesc {
|
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const char *dad_name; /* algorithm name */
|
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void *dad_data; /* opaque algorithm description */
|
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int dad_ninputs; /* number of inputs */
|
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};
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.Ed
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.Pp
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The
|
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.Em dad_name
|
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member points to a valid
|
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.Nm dmover
|
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function name which the client may specify. The
|
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.Em dad_data
|
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member points to a back-end-specific description of the algorithm.
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.Pp
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A back-end presents itself to the
|
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.Nm dmover
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facility using the
|
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.Fa dmover_backend
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structure. The back-end must initialize the following members
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of the structure:
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.Bl -tag -width "XXXX"
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.It const char *dmb_name
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This is the name of the back-end.
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.It u_int dmb_speed
|
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This is an estimate of the number of kilobytes/sec. that the
|
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back-end can process.
|
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.It void *dmb_cookie
|
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This is a pointer to back-end private data.
|
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.It const struct dmover_algdesc *dmb_algdescs
|
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This points to an array of
|
||||
.Fa dmover_algdesc
|
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structures which describe the functions the data mover can perform.
|
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.It int dmb_nalgdescs
|
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This is the number of elements in the
|
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.Em dmb_algdescs
|
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array.
|
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.It void (*dmb_process)(struct dmover_backend *)
|
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This is the entry point to the back-end used to process requests.
|
||||
.El
|
||||
.Pp
|
||||
When invoked by the
|
||||
.Nm dmover
|
||||
facility, the back-end's
|
||||
.Fn (*dmb_process)
|
||||
function should examine the pending request queue in it's
|
||||
.Fa dmover_backend
|
||||
structure:
|
||||
.Bl -tag -width "XXXX"
|
||||
.It TAILQ_HEAD(, dmover_request) dmb_pendreqs
|
||||
This is the queue of pending requests.
|
||||
.It int dmb_npendreqs
|
||||
This is the number of requests in the
|
||||
.Em dmb_pendreqs
|
||||
queue.
|
||||
.El
|
||||
.Pp
|
||||
If an error occurs when processing the request, the
|
||||
.Em DMOVER_REQ_ERROR
|
||||
bit must be set in the
|
||||
.Em dreq_flags
|
||||
member of the request, and the
|
||||
.Em dreq_error
|
||||
member set to an
|
||||
.Xr errno 2
|
||||
value to indicate the error.
|
||||
.Pp
|
||||
When the back-end has finished processing the request, it must call
|
||||
the
|
||||
.Fn dmover_done
|
||||
function. This function eventually invokes the client's call-back
|
||||
routine.
|
||||
.Pp
|
||||
If a hardware-assisted data mover uses interrupts, the interrupt handlers
|
||||
should be registered at IPL_BIO.
|
||||
.Pp
|
||||
The following functions are provided to the back-ends:
|
||||
.Bl -tag -width "XXXX"
|
||||
.It void Fn dmover_backend_register "struct dmover_backend *backend"
|
||||
.Pp
|
||||
The
|
||||
.Fn dmover_backend_register
|
||||
function registers the back-end
|
||||
.Fa backend
|
||||
with the
|
||||
.Nm dmover
|
||||
facility.
|
||||
.It void Fn dmover_backend_unregister "struct dmover_backend *backend"
|
||||
.Pp
|
||||
The
|
||||
.Fn dmover_backend_unregister
|
||||
function removes the back-end
|
||||
.Fa backend
|
||||
from the
|
||||
.Nm dmover
|
||||
facility. The back-end must already be registered.
|
||||
.It void Fn dmover_done "struct dmover_request *req"
|
||||
.Pp
|
||||
The
|
||||
.Fn dmover_done
|
||||
function is called by the back-end when it has finished processing
|
||||
a request, whether the request completed successfully or not.
|
||||
.El
|
||||
.Pp
|
||||
The
|
||||
.Fn dmover_backend_register
|
||||
and
|
||||
.Fn dmover_backend_unregister
|
||||
functions must not be called from interrupt context.
|
||||
.Pp
|
||||
The
|
||||
.Fn dmover_done
|
||||
function may be called at
|
||||
.Em IPL_BIO ,
|
||||
.Em IPL_SOFTCLOCK ,
|
||||
.Em IPL_SOFTNET ,
|
||||
or in non-interrupt context.
|
||||
.Ss EXAMPLE USAGE
|
||||
The following is an example of a client using
|
||||
.Nm dmover
|
||||
to zero-fill a region of memory. In this example, the CPU will be
|
||||
able to context switch to another thread and perform work while the
|
||||
hardware-assisted data mover clears the specified block of memory.
|
||||
.Bd -literal
|
||||
int
|
||||
hw_bzero(void *buf, size_t len)
|
||||
{
|
||||
struct dmover_session *dses;
|
||||
struct dmover_request *dreq;
|
||||
int error;
|
||||
|
||||
error = dmover_session_create(DMOVER_FUNC_ZERO, &dses);
|
||||
if (error)
|
||||
return (error);
|
||||
|
||||
dreq = dmover_request_alloc(dses, NULL);
|
||||
if (dreq == NULL) {
|
||||
dmover_session_destroy(dses);
|
||||
return (ENOMEM);
|
||||
}
|
||||
|
||||
dreq->dreq_flags = DMOVER_REQ_WAIT;
|
||||
dreq->dreq_callback = NULL;
|
||||
dreq->dreq_outbuf.dreq_outbuf_type = DMOVER_BUF_LINEAR;
|
||||
dreq->dreq_outbuf.dreq_outbuf_linear = buf;
|
||||
dreq->dreq_outbuf.dreq_outbuf_len = len;
|
||||
|
||||
dmover_process(dreq);
|
||||
|
||||
error = (dreq->dreq_flags & DMOVER_REQ_ERROR) ?
|
||||
dreq->dreq_error : 0;
|
||||
|
||||
dmover_request_free(dreq, NULL);
|
||||
dmover_session_destroy(dses);
|
||||
|
||||
return (error);
|
||||
}
|
||||
.Ed
|
||||
.Sh SEE ALSO
|
||||
.Xr dmoverio 4 ,
|
||||
.Xr queue 3
|
||||
.Sh HISTORY
|
||||
The
|
||||
.Nm dmover
|
||||
facility first appeared in
|
||||
.Nx 2.0 .
|
||||
.Sh AUTHORS
|
||||
The
|
||||
.Nm dmover
|
||||
facility was designed and implemented by
|
||||
.An Jason R. Thorpe
|
||||
.Aq thorpej@wasabisystems.com
|
||||
and contributed by Wasabi Systems, Inc.
|
||||
.Sh BUGS
|
||||
The mechanism by which a back-end should advertise its performance to
|
||||
the request scheduler is not well-defined. Therefore, the load-balancing
|
||||
mechanism within the request scheduler is also not well-defined.
|
||||
Loading…
Reference in New Issue