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From: Ira Weiny <ira.weiny@intel.com>
To: Leon Romanovsky <leon@leon.nu>
Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
	Dennis Dalessandro <dennis.dalessandro@intel.com>,
	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
Date: Fri, 15 Apr 2016 12:17:55 -0400	[thread overview]
Message-ID: <20160415161754.GA21549@rhel> (raw)
In-Reply-To: <20160415040126.GB10689@leon.nu>

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

  reply	other threads:[~2016-04-15 16:17 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-14 15:41 [PATCH 0/7] IB/hfi1: Remove write() and use ioctl() for user access Dennis Dalessandro
2016-04-14 15:41 ` [PATCH 1/7] IB/hfi1: Export drivers user sw version via sysfs Dennis Dalessandro
2016-04-18 13:05   ` Christoph Hellwig
2016-04-14 15:41 ` [PATCH 2/7] IB/hfi1: Remove unused user command Dennis Dalessandro
2016-04-18 13:05   ` Christoph Hellwig
2016-04-14 15:41 ` [PATCH 3/7] IB/hfi1: Add ioctl() interface for user commands Dennis Dalessandro
2016-04-14 15:41 ` [PATCH 4/7] IB/hfi1: Remove write(), use ioctl() for user cmds Dennis Dalessandro
2016-04-14 15:42 ` [PATCH 5/7] IB/hfi1: Add trace message in user IOCTL handling Dennis Dalessandro
2016-04-14 15:42 ` [PATCH 6/7] IB/hfi1: Consolidate IOCTL defines Dennis Dalessandro
2016-04-14 15:42 ` [PATCH 7/7] IB/hfi1: Move eprom to its own device Dennis Dalessandro
2016-04-14 16:45 ` [PATCH 0/7] IB/hfi1: Remove write() and use ioctl() for user access Jason Gunthorpe
2016-04-14 17:48   ` Ira Weiny
2016-04-14 18:05     ` Jason Gunthorpe
2016-04-14 18:42       ` Dennis Dalessandro
2016-04-14 18:56         ` Jason Gunthorpe
2016-04-15  4:01     ` Leon Romanovsky
2016-04-15 16:17       ` Ira Weiny [this message]
2016-04-15 17:30         ` Leon Romanovsky
2016-04-15 17:34           ` Christoph Hellwig
2016-04-15 17:44             ` Woodruff, Robert J
2016-04-15 21:03               ` Leon Romanovsky
2016-04-15 17:46             ` Hefty, Sean
2016-04-15 21:23             ` Leon Romanovsky
2016-04-15 23:28               ` Ira Weiny
2016-04-16  6:09                 ` Leon Romanovsky
2016-04-16 15:29                   ` Dennis Dalessandro
2016-04-15 23:37               ` Jason Gunthorpe
2016-04-16  6:00                 ` Leon Romanovsky
2016-04-16 19:19                   ` Al Viro
2016-04-18 12:00                     ` Dennis Dalessandro
2016-04-14 17:52   ` Dennis Dalessandro
2016-04-14 18:46     ` Jason Gunthorpe
2016-04-18 13:09   ` Christoph Hellwig
2016-04-18 17:40     ` Jason Gunthorpe
2016-04-18 18:24       ` Christoph Hellwig
2016-04-19  3:45         ` Ira Weiny
2016-04-19 18:40           ` Christoph Hellwig
2016-04-19 17:38         ` Jason Gunthorpe

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