From owner-freebsd-hackers Thu Mar 5 15:12:41 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA06426 for freebsd-hackers-outgoing; Thu, 5 Mar 1998 15:12:41 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from dingo.cdrom.com (dingo.cdrom.com [204.216.28.145]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA06420 for ; Thu, 5 Mar 1998 15:12:31 -0800 (PST) (envelope-from mike@dingo.cdrom.com) Received: from dingo.cdrom.com (localhost [127.0.0.1]) by dingo.cdrom.com (8.8.8/8.8.5) with ESMTP id PAA27042; Thu, 5 Mar 1998 15:07:52 -0800 (PST) Message-Id: <199803052307.PAA27042@dingo.cdrom.com> X-Mailer: exmh version 2.0zeta 7/24/97 To: Ustimenko Semen cc: Mike Smith , freebsd-hackers@FreeBSD.ORG Subject: Re: Are mbufs aligned or bounded on something? In-reply-to: Your message of "Thu, 05 Mar 1998 16:31:54 +0600." Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Thu, 05 Mar 1998 15:07:51 -0800 From: Mike Smith Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > Hello! G'day! > On Wed, 4 Mar 1998, Mike Smith wrote: > > Unless it explicitly matters to your hardware, you should assume that > > mbuf clusters are aligned to suit the architecture you're running on. > > > > If it *does* matter to your hardware, I would be inclined to suggest > > that you code to handle all situations, and optimise for the case where > > the alignment best suits you. This will greatly improve the > > portability of your code. > > > > It realy touch hardware becouse i pass physical address of > mtod( caddr_t, mbuf) to hardware, and if it cross the PAGE_SIZE, DMA > operation will overwrite some physical address that do not belong to > mbuf data area:( Ah. You should look at the fxp driver to see how this is handled. I suspect that you're actually safe to assume that the data area will not cross a page boundary, but you might want to check. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message