From owner-cvs-src@FreeBSD.ORG  Wed Mar  1 23:50:40 2006
Return-Path: <owner-cvs-src@FreeBSD.ORG>
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 527B616A420;
	Wed,  1 Mar 2006 23:50:40 +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 719F343D60;
	Wed,  1 Mar 2006 23:50:37 +0000 (GMT)
	(envelope-from scottl@samsco.org)
Received: from [192.168.254.11] (junior.samsco.home [192.168.254.11])
	(authenticated bits=0)
	by pooker.samsco.org (8.13.4/8.13.4) with ESMTP id k21NoaGI065993;
	Wed, 1 Mar 2006 16:50:36 -0700 (MST)
	(envelope-from scottl@samsco.org)
Message-ID: <4406334F.7070205@samsco.org>
Date: Wed, 01 Mar 2006 16:50:39 -0700
From: Scott Long <scottl@samsco.org>
User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.12) Gecko/20051230
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: John-Mark Gurney <gurney_j@resnet.uoregon.edu>
References: <200602281958.k1SJwvGL051504@repoman.freebsd.org>
	<20060301232621.GF29183@ip.net.ua>
	<20060301233327.GQ840@funkthat.com>
In-Reply-To: <20060301233327.GQ840@funkthat.com>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-Spam-Status: No, score=-1.4 required=3.8 tests=ALL_TRUSTED 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, src-committers@FreeBSD.org,
	Ruslan Ermilov <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 <cvs-src.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-src>
List-Post: <mailto:cvs-src@freebsd.org>
List-Help: <mailto:cvs-src-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 01 Mar 2006 23:50:40 -0000

John-Mark Gurney wrote:
> Ruslan Ermilov wrote this message on Thu, Mar 02, 2006 at 01:26 +0200:
> 
>>On Tue, Feb 28, 2006 at 07:58:57PM +0000, John-Mark Gurney wrote:
>>
>>>jmg         2006-02-28 19:58:57 UTC
>>>
>>>  FreeBSD src repository
>>>
>>>  Modified files:
>>>    share/man/man9       bus_dma.9 
>>>  Log:
>>>  update examples to use the correct terms that was never updated when the
>>>  earlier descriptions were gone over...
>>>  
>>>  MFC after:      3 days
>>>  
>>>  Revision  Changes    Path
>>>  1.32      +3 -3      src/share/man/man9/bus_dma.9
>>>
>>
>>Not enough of fixing: "DMA read" and "DMA write" are also entangled here.
> 
> 
> Nope...  WRITE == DMA read...  Read the descriptions of the flags
> very carefully...  If you aren't confused, you don't understand it..
> The reason you're confused is the reason why everyone gets it wrong,
> and no one ever gets it correct the first time trying to figure out
> which one to use...
> 

Think of it from the perspective of the driver doing an operation.  If 
the driver is reading a block off the disk, then you want to use the
PREREAD/POSTREAD operations.  Likewise for writes.  It is done this way
for clarity in the driver.  I can't imagine how many bugs we'd have if
write == read in the driver sources.

Scott