Re: [Qemu-devel] Missing ARMv6 instructions?

[Jamie Lokier <jamie@shareable.org>]

Paul Brook <paul@codesourcery.com> wrote:
>> qemu cvs only supports ARMv5TE.
>> 
>> The ARMv6 architecture is released under a more restrictive
>> licence than ARMv5.  The Arm licencing department have explicitly
>> prohibited the distribution of open source ARMv6/v7 emulators.
>>
>> > We're trying to get this restriction lifted, but so far to no avail.

Wolfgang Schildbach wrote:
> Thanks, Paul. That explains it...
> I find it strange that ARM would restrict emulation of their architecture 
> -- that could hardly pose a threat to their business, I would say.

I find it strange that they can restrict emulation, if they can.

Perhaps they can't, and maybe they like to send threatening letters to
frighten people away from doing it?

That's not so surprising for ARM.  They halted the development of an
open source ARM-compatible FPGA design too.

What claim does ARM have over software that they don't write and whose
only resemblance is that it speaks the same protocol?

It looks, and smells, like an attempt at "interface copyright".
I.e. to copyright something just for offering a similar interface.

E.g. much the same as Microsoft attempting to stop people implementing
a "task bar".  Yet, Microsoft can't do that, and nobody is afraid of
writing window managers with task bars.

I could understand a claim if someone acquired ARM's documentation
under an agreement to not produce an emulator.  But I don't see how
someone who has no connection with ARM can be restricted by ARM in
that way.

Has ARM ever actually followed through on their threats and _won_ a
case to ban compatible software from being distributed?

And if there is a possibility of that - in which countries do they
have any weight?  Dare I suggest encouraging the development of
patches they don't like to countries where they have no legal weight?

-- Jamie