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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Date:	Tue, 08 Dec 2009 11:30:39 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Andy Walls <awalls@...ix.net>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jarod Wilson <jarod@...sonet.com>,
	Krzysztof Halasa <khc@...waw.pl>,
	Christoph Bartelmus <lirc@...telmus.de>, 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

Andy Walls wrote:
> On Mon, 2009-12-07 at 20:22 -0800, Dmitry Torokhov wrote:
>> On Mon, Dec 07, 2009 at 09:42:22PM -0500, Andy Walls wrote:
> 
>>> 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?
>>>
>> Can you distinguish between the 2 remotes (not receivers)?
> 
> Yes.  RC-6 and RC-5 are different enough to distinguish between the two.
> (Honestly I could pile on more protocols that have similar pulse time
> periods, but that's complexity for no good reason and I don't know of a
> vendor that bundles 3 types of remotes per TV card.)

You'll be distinguishing the protocol, not the remote. If I understood
Dmitry's question, he is asking if you can distinguish between two different
remotes that may, for example, be using both RC-5 or both RC-6 or one RC-5
and another RC-6.

>>  Like I said,
>> I think the preferred way is to represent every remote that can be
>> distinguished from each other as a separate input device.
> 
> OK.  With RC-5, NEC, and RC-6 at least there is also an address or
> system byte or word to distingish different remotes.  However creating
> multiple input devices on the fly for detected remotes would be madness
> - especially with a decoding error in the address bits.  
> 
> Any one vendor usually picks one address for their bundled remote.
> Hauppaugue uses address 0x1e for it's RC-5 remotes AFAICT.

The address field on RC-5 protocol is not meant to distinguish different
vendors, but different "applications". It identifies that a code should
be sent to a TV or a VCR, or a DVD or a SAT.

In the case of bundled IR's, some vendors like Hauppauge opted to use a
reserved address to avoid conflicts with other equipments. It happens that
vendor's "reserved address" can be different between two different vendors,
but is just an educated guess to say that an address equal to 0x1e is Hauppauge.

Cheers,
Mauro.
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