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
next prev parent 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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