Date: Fri, 21 Sep 2001 09:12:10 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: Luigi Rizzo <luigi@info.iet.unipi.it> Cc: hackers@freebsd.org, wpaul@freebsd.org Subject: Re: any reason to use m_devget in the "dc" driver ? Message-ID: <15275.15530.678683.65377@grasshopper.cs.duke.edu> In-Reply-To: <200109210703.JAA57756@info.iet.unipi.it> References: <200109210703.JAA57756@info.iet.unipi.it>
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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
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