[PATCH] dma-buf: Use EXPORT_SYMBOL

[Mauro Carvalho Chehab]

Em Thu, 11 Oct 2012 08:47:15 -0500
Rob Clark <robdclark at gmail.com> escreveu:

> On Thu, Oct 11, 2012 at 6:13 AM, Mauro Carvalho Chehab
> <mchehab at redhat.com> wrote:
> > Em Thu, 11 Oct 2012 09:20:12 +0200
> > Hans Verkuil <hverkuil at xs4all.nl> escreveu:
> >
> >> > my understaning is
> >> > that the drivers/media/ authors should also ack with this licensing
> >> > (possible) change. I am one of the main contributors there. Alan also has
> >> > copyrights there, and at other parts of the Linux Kernel, including the driver's
> >> > core, from where all Linux Kernel drivers are derivative work, including this one.
> >> >
> >> > As Alan well said, many other core Linux Kernel authors very likely share
> >> > this point of view.
> >> >
> >> > So, developers implicitly or explicitly copied in this thread that might be
> >> > considering the usage of dmabuf on proprietary drivers should consider
> >> > this email as a formal notification of my viewpoint: e. g. that I consider
> >> > any attempt of using DMABUF or media core/drivers together with proprietary
> >> > Kernelspace code as a possible GPL infringement.
> >>
> >> As long as dmabuf uses EXPORT_SYMBOL_GPL that is definitely correct. Does your
> >> statement also hold if dmabuf would use EXPORT_SYMBOL? (Just asking)
> >
> > If you read the Kernel COPYING file, it is explicitly said there that the Kernel
> > is licensing with GPLv2. The _ONLY_ exception there is the allowance to use
> > the kernel via normal syscalls:
> >
> >            "NOTE! This copyright does *not* cover user programs that use kernel
> >          services by normal system calls - this is merely considered normal use
> >          of the kernel, and does *not* fall under the heading of "derived work".
> >          Also note that the GPL below is copyrighted by the Free Software
> >          Foundation, but the instance of code that it refers to (the Linux
> >          kernel) is copyrighted by me and others who actually wrote it."
> >
> > The usage of EXPORT_SYMBOL() is not covered there, so those symbols are also
> > covered by GPLv2.
> >
> > As the usage of a kernel symbol by a proprietary driver is not explicitly
> > listed there as a GPLv2 exception, the only concrete results of this patch is
> > to spread FUD, as EXPORT_SYMBOL might generate some doubts on people that
> > don't read the Kernel's COPYING file.
> >
> > With or without this patch, anyone with intelectual rights in the Kernel may
> > go to court to warrant their rights against the infringing closed source drivers.
> > By not making it explicitly, you're only trying to fool people that using
> > it might be allowed.
> 
> Maybe a dumb question (I'm a programmer, not a lawyer), but does it
> change anything if we make the APIs related to *exporting* a dmabuf as
> EXPORT_SYMBOL() and keep the APIs related to *importing* as
> EXPORT_SYMBOL_GPL().  This at least avoids the non-GPL kernel module
> from calling in to other driver code, while still allowing the non-GPL
> driver to export a buffer that GPL drivers could use.


IANAL. My understanding is that nothing changes by using either programmer's
dialect: it sounds doubtful that the court would actually take a look
into the Kernel's source code: they're lawyers, not programmers, and
both clauses are just Kernel's source code. Nothing more, nothing less:

EXPORT_SYMBOL, is not EXPORT_SYMBOL_BSD (or similar): this syntax
doesn't bring _any_kind_ of additional licensing rights. That means that
the licensing terms that apply there are just the ones stated at COPYING
file.

So, in any case, the court will judge the allegations based at the Kernel
licensing terms, and will seek if the terms of such licensing were
violated. The court will also likely use formal notifications of
potential infringements, like the ones in this thread, and other
non-technical documents, like meeting reports, email threads, etc,
in order to check who has intelectual rights on the Linux Kernel,
and if the ones that violated the rights did it by purpose.

Regards,
Mauro