From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 9 Jan 2001 20:37:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 9 Jan 2001 20:37:36 -0500 Received: from pizda.ninka.net ([216.101.162.242]:5258 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id ; Tue, 9 Jan 2001 20:37:32 -0500 Date: Tue, 9 Jan 2001 17:20:08 -0800 Message-Id: <200101100120.RAA07805@pizda.ninka.net> From: "David S. Miller" To: jgarzik@mandrakesoft.com CC: linux-kernel@vger.kernel.org, netdev@oss.sgi.com In-Reply-To: <3A5BB985.8A249BE1@mandrakesoft.com> (message from Jeff Garzik on Tue, 09 Jan 2001 20:23:17 -0500) Subject: Re: Updated zerocopy patch up on kernel.org In-Reply-To: <200101100055.QAA07674@pizda.ninka.net> <3A5BB985.8A249BE1@mandrakesoft.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Date: Tue, 09 Jan 2001 20:23:17 -0500 From: Jeff Garzik Is there any value to supporting fragments in a driver which doesn't do hardware checksumming? IIRC Alexey had a patch to do such for Tulip, but I don't see it in the above patchset. I'm actually considering making the SG w/o hwcsum situation illegal. Basically, with SG only, you can run into some problems. We don't prevent anyone from making modifications to the paged data, we just grab references to the pages. This works perfectly fine when the card does the checksumming, the card DMAs a snapshot of the data into it's internal buffers, checksums that local snapshot of the data, and the checksum is fine. If, on the other hand, we're doing this in software, we can send out packets with bad checksums. The next retransmit could fix it up, but this is a horrible scheme quality of implementation wise. Later, David S. Miller davem@redhat.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/