linux-kernel - Re: [PATCH 0/7] IB/hfi1: Remove write() and use ioctl() for user access

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Message-ID: <20160418174047.GB13865@obsidianresearch.com>
Date:	Mon, 18 Apr 2016 11:40:47 -0600
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Dennis Dalessandro <dennis.dalessandro@...el.com>,
	dledford@...hat.com, linux-rdma@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, torvalds@...ux-foundation.org,
	viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/7] IB/hfi1: Remove write() and use ioctl() for user
 access

On Mon, Apr 18, 2016 at 06:09:09AM -0700, Christoph Hellwig 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 looked through the patches I tend to disagree - while we should wait
> for a global UAPI for anything that's actually RDMA/verbs related these
> seem to be misc little bits specific to the driver that have no business
> in any sort of generic RDMA API.

I wasn't arguing this should integrate into verbs in some way, only
that the way to access the driver-specific uAPI of a RDMA device should
be through the RDMA common uAPI and not through a random char dev.

.. and of course that the driver-specific API be subject to a sane
review and use of the normal standards, not just written off as
driver-garbage nobody cares about. :(

For instance, if we had a driver specific channel, it casts this
endless stream of uAPI verbs patches in a different light: maybe they
should go down the driver-specific channel instead.

Jason