From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752682AbcDOQSX (ORCPT ); Fri, 15 Apr 2016 12:18:23 -0400 Received: from mga09.intel.com ([134.134.136.24]:27154 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751962AbcDOQSU (ORCPT ); Fri, 15 Apr 2016 12:18:20 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,488,1455004800"; d="scan'208";a="686860557" Date: Fri, 15 Apr 2016 12:17:55 -0400 From: Ira Weiny To: Leon Romanovsky Cc: Jason Gunthorpe , Dennis Dalessandro , dledford@redhat.com, linux-rdma@vger.kernel.org, linux-fsdevel@vger.kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/7] IB/hfi1: Remove write() and use ioctl() for user access Message-ID: <20160415161754.GA21549@rhel> References: <20160414153727.6387.96381.stgit@scvm10.sc.intel.com> <20160414164550.GC6247@obsidianresearch.com> <20160414174830.GA11641@rhel.sc.intel.com> <20160415040126.GB10689@leon.nu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160415040126.GB10689@leon.nu> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 15, 2016 at 07:01:26AM +0300, Leon Romanovsky wrote: > On Thu, Apr 14, 2016 at 01:48:31PM -0400, Ira Weiny wrote: > > On Thu, Apr 14, 2016 at 10:45:50AM -0600, Jason Gunthorpe wrote: > > > On Thu, Apr 14, 2016 at 08:41:35AM -0700, Dennis Dalessandro wrote: > > > > This patch series removes the write() interface for user access in favor of an > > > > ioctl() based approach. This is in response to the complaint that we had > > > > different handlers for write() and writev() doing different things and expecting > > > > different types of data. See: > > > > > > I think we should wait on applying these patches until we globally sort out > > > what to do with the rdma uapi. > > > > > > It just doesn't make alot of sense for drivers to have their own personal > > > char devices. :( > > > > I'm afraid I have to disagree at this time. Someday we may have "1 char device > > to rule them all" but right now we don't have any line of sight to that > > solution. It may be _years_ before we can agree to the semantics which will > > work for all high speed, kernel bypass, rdma, low latency, network devices. > > You didn't ever try to come and work on the solution. We talked about > finite time frame (_months_) which is doable based on knowledge that user > space parts are developed by the same companies and all our future changes > will be in one subsystem. How can you say that I am not working on a solution? We spent most of last week discussing possible solutions and I am in support of a more common core. But ask yourself this. If hfi1 did not support verbs at all would this even be an issue? > > You were supposed to prepare "wish list" from this new API as an initial > phase. If you do it, you will find that it is very short and in the > initial meeting you will see that it similar to other participants in > linux-rdma community. The list of operations may be short. But the way in which you do those in a performant way for each hardware device is _very_ different. This is a problem which has been debated for years and no one has come up with an elegant solution. Every solution ends up being, to quote a presenter at last weeks conference, "shoving a square peg into a round hole". Until we all admit 2 things. 1) That there are devices which don't operate on QPs 2) That the High Speed interconnect core should present something more abstract than a QP interface we are not really creating a common layer. I do admit Jasons idea has some merit but I'm just not sure it provides so much benefit that it is worth the effort at this time. Ira