From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Erdfelt Subject: Re: [RFC] tulip VLAN support Date: Wed, 5 Jan 2005 14:31:47 -0800 Message-ID: <20050105223147.GE18847@sventech.com> References: <20050105193425.GY18847@sventech.com> <41DC6669.9090407@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@oss.sgi.com Return-path: To: Jeff Garzik Content-Disposition: inline In-Reply-To: <41DC6669.9090407@pobox.com> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Wed, Jan 05, 2005, Jeff Garzik wrote: > Johannes Erdfelt wrote: > >@@ -259,7 +259,7 @@ > > #define RX_RING_SIZE 128 > > #define MEDIA_MASK 31 > > > >-#define PKT_BUF_SZ 1536 /* Size of each temporary Rx buffer. > >*/ > >+#define PKT_BUF_SZ 1540 /* Size of each temporary Rx buffer. > >*/ > > This is the reason why the tulip "vlan" patch is continually rejected. > You shouldn't need to increase this constant, but rather follow the > other "large MTU" driver conversions. Donald replied to my privately with a number of reasons why similar patches have been rejected and this one of the same points brought up. I just copied the 2.4 patch that worked so well for me, but I was curious about this part of the patch as well. I asked Donald this, but I guess I'll ask on the list here too. If the point of PKT_BUF_SZ is to keep a consistent buffer size between drivers (for performance reasons), why isn't this value defined in a standard header? > Donald Becker's tulip.c (on which the kernel tulip is based) supports > proper MTU changing: ftp://ftp.scyld.com/pub/network/ The problem isn't changing the MTU, it's that a full ethernet sized packet along with the 802.1q tagging causes the size of the packet to grow past the size the driver (and it looks like the chip) will allow. The driver on Donald's site looks to have the same problem as the driver in the kernel. I'm still trying to find some specs on the tulip interface so I can better understand the chip and the changes necessary to fix this problem. Anyone have any pointers? JE