linux-kernel - Re: [RFC] Should we create a raw input interface for IR's ? - Was: Re: [PATCH 1/3 v2] lirc core device driver infrastructure

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Message-Id: <1260240142.3086.14.camel@palomino.walls.org>
Date:	Mon, 07 Dec 2009 21:42:22 -0500
From:	Andy Walls <awalls@...ix.net>
To:	Jarod Wilson <jarod@...sonet.com>
Cc:	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Krzysztof Halasa <khc@...waw.pl>,
	Christoph Bartelmus <lirc@...telmus.de>,
	dmitry.torokhov@...il.com, j@...nau.net, jarod@...hat.com,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, superm1@...ntu.com
Subject: Re: [RFC] Should we create a raw input interface for IR's ? - Was:
 Re: [PATCH 1/3 v2] lirc core device driver infrastructure

On Mon, 2009-12-07 at 13:19 -0500, Jarod Wilson wrote:
> On Nov 26, 2009, at 2:43 PM, Andy Walls wrote:
> 
> > On Thu, 2009-11-26 at 12:05 -0200, Mauro Carvalho Chehab wrote:
> >> Krzysztof Halasa wrote:
> >>> Andy Walls <awalls@...ix.net> writes:
> >>> 
> >>>> I would also note that RC-6 Mode 6A, used by most MCE remotes, was
> >>>> developed by Philips, but Microsoft has some sort of licensing interest
> >>>> in it and it is almost surely encumbered somwhow:
> >>> 
> >>> I don't know about legal problems in some countries but from the
> >>> technical POV handling the protocol in the kernel is more efficient
> >>> or (/and) simpler.
> >> 
> >> A software licensing from Microsoft won't apply to Linux kernel, so I'm
> >> assuming that you're referring to some patent that they could be filled
> >> about RC6 mode 6A.
> >> 
> >> I don't know if is there any US patent pending about it (AFAIK, only US
> >> accepts software patents), but there are some prior-art for IR key
> >> decoding. So, I don't see what "innovation" RC6 would be adding. 
> >> If it is some new way to transmit waves, the patent issues
> >> aren't related to software, and the device manufacturer had already handled
> >> it when they made their devices.
> >> 
> >> If it is just a new keytable, this issue 
> >> could be easily solved by loading the keytable via userspace.
> >> 
> >> Also, assuming that you can use the driver only with a hardware that comes
> >> with a licensed software, the user has already the license for using it.
> >> 
> >> Do you have any details on what patents they are claiming?
> > 
> > The US Philips RC-6 patent is US Patent 5,877,702
> > 
> > http://www.google.com/patents?vid=USPAT5877702
> > 
> > Click on download PDF to get a copy of the whole patent.
> > 
> > I am not a lawyer.  Philips claims' all appear to tie to a transmitter
> > or receiver as part of a system, but most of the claims are about
> > information and bit positions and lengths.
> ...
> > IMO, given
> > 
> > a. the dearth of public information about RC-6, indicating someone
> > thinks it's their trade secret or intellectual property
> > 
> > b. Microsoft claiming to license something related to the MCE remote
> > protocols (which are obviously RC-6 Mode 6A),
> > 
> > c. my inability to draw a "clear, bright line" that RC-6 Mode 6A
> > encoding and decoding, as needed by MCE remotes, implemented in software
> > doesn't violate anyone's government granted rights to exclusivity.
> > 
> > I think it's much better to implement software RC-6 Mode 6A encoding and
> > decoding in user space, doing only the minimum needed to get the
> > hardware setup and going in the kernel.  
> > 
> > Encoding/decoding of RC-6 by microcontrollers with firmware doesn't
> > worry me. 
> > 
> > 
> > Maybe I'm being too conservative here, but I have a personal interest in
> > keeping Linux free and unencumbered even in the US which, I cannot deny,
> > has a patent system that is screwed up.
> 
> So I had one of the people who does all the license and patent audits
> for Fedora packages look at the Philips patent on RC-6. He's 100%
> positive that the patent *only* covers hardware, there should be no
> problem whatsoever writing a software decoder for RC-6.

OK.  Thanks for having some professionals take a look.  (I'm assuming
that's the only patent.)

So I'll whip up an RC-6 Mode 6A decoder for cx23885-input.c before the
end of the month.

I can setup the CX2388[58] hardware to look for both RC-5 and RC-6 with
a common set of parameters, so I may be able to set up the decoders to
handle decoding from two different remote types at once.  The HVR boards
can ship with either type of remote AFAIK.

I wonder if I can flip the keytables on the fly or if I have to create
two different input devices?

Regards,
Andy

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