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Date:	Fri, 20 Jun 2014 07:50:47 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Rob Clark <robdclark@...il.com>, linux-arch@...r.kernel.org,
	Thomas Hellstrom <thellstrom@...are.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
	Colin Cross <ccross@...gle.com>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>
Subject: Re: [REPOST PATCH 1/8] fence: dma-buf cross-device synchronization (v17)

On 20 June 2014 04:19, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Thu, Jun 19, 2014 at 01:45:30PM -0400, Rob Clark wrote:
>> On Thu, Jun 19, 2014 at 1:00 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
>> > On Thu, Jun 19, 2014 at 10:00:18AM -0400, Rob Clark wrote:
>> >> On Wed, Jun 18, 2014 at 9:13 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
>> >> > On Wed, Jun 18, 2014 at 12:36:54PM +0200, Maarten Lankhorst wrote:
>> >> >> +#define CREATE_TRACE_POINTS
>> >> >> +#include <trace/events/fence.h>
>> >> >> +
>> >> >> +EXPORT_TRACEPOINT_SYMBOL(fence_annotate_wait_on);
>> >> >> +EXPORT_TRACEPOINT_SYMBOL(fence_emit);
>> >> >
>> >> > Are you really willing to live with these as tracepoints for forever?
>> >> > What is the use of them in debugging?  Was it just for debugging the
>> >> > fence code, or for something else?
>> >> >
>> >> >> +/**
>> >> >> + * fence_context_alloc - allocate an array of fence contexts
>> >> >> + * @num:     [in]    amount of contexts to allocate
>> >> >> + *
>> >> >> + * This function will return the first index of the number of fences allocated.
>> >> >> + * The fence context is used for setting fence->context to a unique number.
>> >> >> + */
>> >> >> +unsigned fence_context_alloc(unsigned num)
>> >> >> +{
>> >> >> +     BUG_ON(!num);
>> >> >> +     return atomic_add_return(num, &fence_context_counter) - num;
>> >> >> +}
>> >> >> +EXPORT_SYMBOL(fence_context_alloc);
>> >> >
>> >> > EXPORT_SYMBOL_GPL()?  Same goes for all of the exports in here.
>> >> > Traditionally all of the driver core exports have been with this
>> >> > marking, any objection to making that change here as well?
>> >>
>> >> tbh, I prefer EXPORT_SYMBOL()..  well, I'd prefer even more if there
>> >> wasn't even a need for EXPORT_SYMBOL_GPL(), but sadly it is a fact of
>> >> life.  We already went through this debate once with dma-buf.  We
>> >> aren't going to change $evil_vendor's mind about non-gpl modules.  The
>> >> only result will be a more flugly convoluted solution (ie. use syncpt
>> >> EXPORT_SYMBOL() on top of fence EXPORT_SYMBOL_GPL()) just as a
>> >> workaround, with the result that no-one benefits.
>> >
>> > It has been proven that using _GPL() exports have caused companies to
>> > release their code "properly" over the years, so as these really are
>> > Linux-only apis, please change them to be marked this way, it helps
>> > everyone out in the end.
>>
>> Well, maybe that is the true in some cases.  But it certainly didn't
>> work out that way for dma-buf.  And I think the end result is worse.
>>
>> I don't really like coming down on the side of EXPORT_SYMBOL() instead
>> of EXPORT_SYMBOL_GPL(), but if we do use EXPORT_SYMBOL_GPL() then the
>> result will only be creative workarounds using the _GPL symbols
>> indirectly by whatever is available via EXPORT_SYMBOL().  I don't
>> really see how that will be better.
>
> You are saying that you _know_ companies will violate our license, so
> you should just "give up"?  And how do you know people aren't working on
> preventing those "indirect" usages as well?  :)
>
> Sorry, I'm not going to give up here, again, it has proven to work in
> the past in changing the ways of _very_ large companies, why stop now?

I've found large companies shipping lots of hw putting pressure on
other large/small companies seems to be only way this has ever
happened, we'd like to cover that up and say its some great GPL
enforcement thing.

To be honest, author's choice is how I'd treat this.

Personally I think _GPL is broken by design, and that Linus's initial
point for them has been so diluted by random lobby groups asking for
every symbol to be _GPL that they are becoming effectively pointless
now. I also dislike the fact that the lobby groups don't just bring
violators to court. I'm also sure someone like the LF could have a
nice income stream if Linus gave them permission to enforce his
copyrights.

But anyways, has someone checked that iOS or Windows don't have a
fence interface? so we know that this is a Linux only interface and
any works using it are derived? Say the nvidia driver isn't a derived
work now, will using this interface magically translate it into a
derived work, so we can go sue them? I don't think so.

But its up to Maarten and Rob, and if they say no _GPL then I don't
think we should be overriding authors intents.

Dave.
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