Date:	Mon, 18 Oct 2010 23:33:39 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Dave Airlie <airlied@...il.com>
Cc:	Greg KH <greg@...ah.com>, codalist@...emann.coda.cs.cmu.edu,
	autofs@...ux.kernel.org, Samuel Ortiz <samuel@...tiz.org>,
	Jan Kara <jack@...e.cz>,
	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>,
	Arnd Bergmann <arnd@...db.de>,
	Jan Harkes <jaharkes@...cmu.edu>, netdev@...r.kernel.org,
	Anders Larsen <al@...rsen.net>, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	Bryan Schumaker <bjschuma@...app.com>,
	Christoph Hellwig <hch@...radead.org>,
	ksummit-2010-discuss@...ts.linux-foundation.org,
	Petr Vandrovec <vandrove@...cvut.cz>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-fsdevel@...r.kernel.org,
	Evgeniy Dushistov <dushistov@...l.ru>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Hendry <andrew.hendry@...il.com>,
	linux-media@...r.kernel.org
Subject: Re: [Ksummit-2010-discuss] [v2] Remaining BKL users, what to do

On Tue, 2010-10-19 at 12:45 +1000, Dave Airlie wrote:
> On Tue, Oct 19, 2010 at 12:24 PM, Greg KH <greg@...ah.com> wrote:

> > So, there is no need for the i830 driver?  Can it just be removed
> > because i915 works instead?
> 
> No because it provides a different userspace ABI to the i915 driver to
> a different userspace X driver etc.
> 
> like I'm sure the intersection of this driver and reality are getting
> quite limited, but its still a userspace ABI change and needs to be
> treated as such. Xorg 6.7 and XFree86 4.3 were the last users of the
> old driver/API.

Thus, you are saying that this will break for people with older user
apps and have a newer kernel?

> 
> >> So it really only leaves the problem case of what do distros do if we
> >> mark things as BROKEN_ON_SMP, since no distro builds UP kernels and
> >> when you boot the SMP kernels on UP they don't run as SMP so not
> >> having the driver load on those is a problem. Maybe we just need some
> >> sort of warn on smp if a smp unfriendly driver is loaded and we
> >> transition to SMP mode. Though this sounds like either (a) something
> >> we do now and I don't about it, (b) work.
> >
> > So you are saying that just because distros will never build such a
> > thing, we should keep it building for SMP mode?  Why not prevent it from
> > being built and if a distro really cares, then they will pony up the
> > development to fix the driver up?
> 
> Distros build the driver now even it it didn't work on SMP it wouldn't
> matter to the 99% of people who have this hw since it can't suppport
> SMP except in some corner cases. So not building for SMP is the same
> as just throwing it out of the kernel since most people don't run
> kernel.org kernels, and shouldn't have to just to get a driver for
> some piece of hardware that worked fine up until now.

Ah! Exactly! Thus, those that do not run kernel.org kernels are using a
distro kernel. Wont these same people use the distro userspace? That is,
if they have upgraded their kernel, most likely, they also update their
X interface.

> 
> Look at this from a user who has this hardware pov, it works for them
> now with a distro kernel, us breaking it isn't going to help that user
> or make any distro care, its just going to screw over the people who
> are actually using it.

But they can use the i915 driver instead, because they are using the
newer userspace apps.

> 
> > In other words, if someone really cares, then they will do the work,
> > otherwise why worry?  Especially as it seems that no one here is going
> > to do it, right?
> 
> Well the thing is doing the work right is a non-trivial task and just
> dropping support only screws the people using the hardware,
> it doesn't place any burden on the distro developers to fix it up. If
> people are really serious about making the BKL go away completely, I
> think the onus should be on them to fix the drivers not on the users
> who are using it, like I'm  guessing if this gets broken the bug will
> end up in Novell or RH bugzilla in a year and nobody will ever see it.

Well the problem comes down to testing it. I don't know of any developer
that is removing the BKL that actually owns hardware to test out these
broken drivers. And for the change not being trivial, means that there's
no way to do in correctly.

-- Steve



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