From owner-freebsd-hackers Fri Sep 21 6:14: 8 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from duke.cs.duke.edu (duke.cs.duke.edu [152.3.140.1]) by hub.freebsd.org (Postfix) with ESMTP id E987A37B405; Fri, 21 Sep 2001 06:14:05 -0700 (PDT) Received: from grasshopper.cs.duke.edu (grasshopper.cs.duke.edu [152.3.145.30]) by duke.cs.duke.edu (8.9.3/8.9.3) with ESMTP id JAA10693; Fri, 21 Sep 2001 09:12:36 -0400 (EDT) Received: (from gallatin@localhost) by grasshopper.cs.duke.edu (8.11.3/8.9.1) id f8LDCAR26996; Fri, 21 Sep 2001 09:12:10 -0400 (EDT) (envelope-from gallatin@cs.duke.edu) From: Andrew Gallatin MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15275.15530.678683.65377@grasshopper.cs.duke.edu> Date: Fri, 21 Sep 2001 09:12:10 -0400 (EDT) To: Luigi Rizzo Cc: hackers@freebsd.org, wpaul@freebsd.org Subject: Re: any reason to use m_devget in the "dc" driver ? In-Reply-To: <200109210703.JAA57756@info.iet.unipi.it> References: <200109210703.JAA57756@info.iet.unipi.it> X-Mailer: VM 6.75 under 21.1 (patch 12) "Channel Islands" XEmacs Lucid Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Luigi Rizzo writes: > Does anyone know of specific reasons to use m_devget() > to extract received packets from the rx buffer in the "dc" > driver, as opposed to passing up the mbuf and just > replacing it with a fresh one in the controller's queue ? > > Other drivers just happily do the latter, including the "de" > driver, so there seems to be no problem with the chipset > in handling this ? I imagine that this was done to follow alignment constraints on non-i386 platforms where having the ip header misaligned is fatal. (the tulip is not capable of byte granularity DMA, so you can't intentionally misalign the ethernet header & end up with an aligned IP header) I imagine the i386 should be made an exception. See rev 1.17 of sys/dev/nge/if_nge.c Drew To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message