From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve Wise Subject: Re: [PATCH V2] libibverbs: Allow arbitrary int values for MTU Date: Wed, 17 Jul 2013 16:44:03 -0500 Message-ID: <51E71023.2060006@opengridcomputing.com> References: <1372768306-6786-1-git-send-email-jsquyres@cisco.com> <20130708172621.GA3852@obsidianresearch.com> <1828884A29C6694DAF28B7E6B8A82373805AAB74@ORSMSX109.amr.corp.intel.com> <20130716144747.GA7304@obsidianresearch.com> <1828884A29C6694DAF28B7E6B8A82373805AECC0@ORSMSX109.amr.corp.intel.com> <1828884A29C6694DAF28B7E6B8A82373805B941D@ORSMSX109.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1828884A29C6694DAF28B7E6B8A82373805B941D-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Hefty, Sean" Cc: "Jeff Squyres (jsquyres)" , Jason Gunthorpe , Roland Dreier , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Doug Ledford List-Id: linux-rdma@vger.kernel.org On 7/17/2013 4:41 PM, Hefty, Sean wrote: >> I hadn't looked at the kernel side yet; I was waiting for the userspace side to >> sort itself out first. > I think it makes sense to start with how user space can get the data. Without eating up reserved fields, we're starting with 8 bit values. > >> Hmm. 16 bits is probably enough for the MTU values, but still, changing kern- >> abi.h will be problematic from an ABI perspective. Do people care about the >> kernel ABI, or is that mainly a userspace issue? > Well, we definitely care about the kernel to user ABI. > > I can't imagine that we're dealing with more than a handful of actual MTU values. Maybe the simplest thing is to extend the mtu enum to include what new values are needed, plus add a function to convert it. (Can we call mulligan?) > > I don't know how iwarp handles this. Does it just report the wrong mtu, since it doesn't necessarily matter? Steve - any idea here? The iwarp drivers just report the nearest mtu enum. Apps don't need it for iwarp like they do for ib. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html