From owner-freebsd-hackers@FreeBSD.ORG  Sat May 30 13:45:58 2015
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id B13D82F8
 for <freebsd-hackers@freebsd.org>; Sat, 30 May 2015 13:45:58 +0000 (UTC)
 (envelope-from ian@freebsd.org)
Received: from outbound3.ore.mailhop.org (erouter6.ore.mailhop.org
 [54.187.213.119]) by mx1.freebsd.org (Postfix) with SMTP id 90CF91609
 for <freebsd-hackers@freebsd.org>; Sat, 30 May 2015 13:45:58 +0000 (UTC)
 (envelope-from ian@freebsd.org)
Received: from ilsoft.org (unknown [73.34.117.227])
 by outbound3.ore.mailhop.org (Halon Mail Gateway) with ESMTPSA;
 Sat, 30 May 2015 13:45:11 +0000 (UTC)
Received: from revolution.hippie.lan (revolution.hippie.lan [172.22.42.240])
 by ilsoft.org (8.14.9/8.14.9) with ESMTP id t4UDjo2J022030;
 Sat, 30 May 2015 07:45:50 -0600 (MDT) (envelope-from ian@freebsd.org)
Message-ID: <1432993550.1200.104.camel@freebsd.org>
Subject: Re: Difference b/w xfer_len and len fields
From: Ian Lepore <ian@freebsd.org>
To: Pratik Singhal <ps06756@gmail.com>
Cc: freebsd-hackers <freebsd-hackers@freebsd.org>
Date: Sat, 30 May 2015 07:45:50 -0600
In-Reply-To: <CAGf2gkMuL0JDnX5PRvWKRSnmAHOFY4jzQEOjM6MQ8u9G4FuLbA@mail.gmail.com>
References: <CAGf2gkMuL0JDnX5PRvWKRSnmAHOFY4jzQEOjM6MQ8u9G4FuLbA@mail.gmail.com>
Content-Type: text/plain; charset="us-ascii"
X-Mailer: Evolution 3.12.10 FreeBSD GNOME Team Port 
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
 <freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-hackers>, 
 <mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers/>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
 <mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 30 May 2015 13:45:58 -0000

On Sat, 2015-05-30 at 11:26 +0530, Pratik Singhal wrote:
> What is the difference b/w the xfer_len and the len fields in the struct
> mmc_data in file sys/dev/mmc/mmcreg.h  ?
> 
> AFAIK , len is the length of the data present in mmc_data , what is
> xfer_len ?
> 

The xfer_len field has historically been unused, until recently.  When
the dwc mmc driver was added, it uses xfer_len as a driver-internal
variable to track how much of the overal work is done as the IO
proceeds.

-- Ian