Date: Thu, 05 Mar 1998 15:07:51 -0800 From: Mike Smith <mike@smith.net.au> To: Ustimenko Semen <semen@iclub.nsu.ru> Cc: Mike Smith <mike@smith.net.au>, freebsd-hackers@FreeBSD.ORG Subject: Re: Are mbufs aligned or bounded on something? Message-ID: <199803052307.PAA27042@dingo.cdrom.com> In-Reply-To: Your message of "Thu, 05 Mar 1998 16:31:54 %2B0600." <Pine.BSF.3.96.980305162255.18429A-100000@iclub.nsu.ru>
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> 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
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