From owner-cvs-src@FreeBSD.ORG Thu Mar 2 22:25:34 2006 Return-Path: X-Original-To: cvs-src@FreeBSD.org Delivered-To: cvs-src@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 2FB5616A427; Thu, 2 Mar 2006 22:25:34 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.FreeBSD.org (Postfix) with ESMTP id D392043D48; Thu, 2 Mar 2006 22:25:30 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from [10.10.3.185] ([69.15.205.254]) (authenticated bits=0) by pooker.samsco.org (8.13.4/8.13.4) with ESMTP id k22MPM1m073097; Thu, 2 Mar 2006 15:25:22 -0700 (MST) (envelope-from scottl@samsco.org) Message-ID: <440770CC.50001@samsco.org> Date: Thu, 02 Mar 2006 15:25:16 -0700 From: Scott Long User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.12) Gecko/20060206 X-Accept-Language: en-us, en MIME-Version: 1.0 To: "M. Warner Losh" References: <20060302071849.GH29183@ip.net.ua> <20060302181629.GS840@funkthat.com> <20060302185507.GM29183@ip.net.ua> <20060302.141520.53336566.imp@bsdimp.com> In-Reply-To: <20060302.141520.53336566.imp@bsdimp.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=0.0 required=3.8 tests=none autolearn=failed version=3.1.0 X-Spam-Checker-Version: SpamAssassin 3.1.0 (2005-09-13) on pooker.samsco.org Cc: cvs-src@FreeBSD.org, gurney_j@resnet.uoregon.edu, src-committers@FreeBSD.org, ru@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/share/man/man9 bus_dma.9 X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Mar 2006 22:25:34 -0000 M. Warner Losh wrote: > Here's what I came up with earlier in the week. > > Index: bus_dma.9 > =================================================================== > RCS file: /home/ncvs/src/share/man/man9/bus_dma.9,v > retrieving revision 1.31 > diff -u -r1.31 bus_dma.9 > --- bus_dma.9 13 Dec 2005 17:07:52 -0000 1.31 > +++ bus_dma.9 2 Mar 2006 21:14:40 -0000 > @@ -265,14 +265,41 @@ > .It Dv BUS_DMASYNC_PREREAD > Perform any synchronization required prior to an update of host memory by the > DMA read operation. > +.Pp > +In other words, the driver is about to command the device to start > +a DMA operation that transfers data from the > +device to the memory described by this map. > +And pending writes to this part of memory that the CPU might have queued > +up will either be discarded or be completed after this operation completes. > .It Dv BUS_DMASYNC_PREWRITE > Perform any synchronization required after an update of host memory by the CPU > and prior to DMA write operations. > +.Pp > +In other words, the CPU flushes any cached writes to the area of memory > +described by this map so they are visible when the device does its > +DMA READ operation on the memory described by the map. > +An implementation may also use this to implement bounce buffers and > +memory barriers. > .It Dv BUS_DMASYNC_POSTREAD > Perform any synchronization required after DMA read operations and prior to > CPU access to host memory. > +.Pp > +In other words, the CPU discards the cached values for the memory range > +described by the map. > +Future reads to the memory range described by the map will fetch the values > +from memory. > +An implementation is free to reload the cache before any driver initiated > +reads to this memory. > +An implementation may also use this to implement bounce buffers and > +memory barriers. > .It Dv BUS_DMASYNC_POSTWRITE > Perform any synchronization required after DMA write operations. > +.Pp > +In other words, this is completely useless. > +The driver writer has noticed that the device has indicated the DMA READ > +operation has completed. > +It is theoretically possible that this would cause the device to do something > +but it is unclear what. > .El > .It Vt bus_dma_lock_t > Client specified lock/mutex manipulation method. Pretty much factually correct, but not the kind of thing that I would commit to a man page. Scott