linux-kernel - Re: [RFC] What are the goals for the architecture of an in-kernel IR system?

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Message-ID: <4B1E6935.207@redhat.com>
Date:	Tue, 08 Dec 2009 12:56:53 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Jon Smirl <jonsmirl@...il.com>
CC:	Krzysztof Halasa <khc@...waw.pl>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	hermann pitton <hermann-pitton@...or.de>,
	Christoph Bartelmus <lirc@...telmus.de>, awalls@...ix.net,
	j@...nau.net, jarod@...hat.com, jarod@...sonet.com,
	kraxel@...hat.com, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	superm1@...ntu.com
Subject: Re: [RFC] What are the goals for the architecture of an in-kernel
 IR 	system?

Jon Smirl wrote:
> On Tue, Dec 8, 2009 at 6:17 AM, Mauro Carvalho Chehab
> <mchehab@...hat.com> wrote:
>> Jon Smirl wrote:
>>> On Mon, Dec 7, 2009 at 6:44 PM, Mauro Carvalho Chehab
>>> <mchehab@...hat.com> wrote:
>>>>> Where is the documentation for the protocol?
>>>> I'm not sure what you're meaning here. I've started a doc about IR at the media
>>> What is the format of the pulse stream data coming out of the lirc device?
>> AFAIK, it is at:
>>        http://www.lirc.org/html/index.html
>>
>> It would be nice to to add it to DocBook after integrating the API in kernel.
>>
> 
> The point of those design review questions was to illustrate that the
> existing LIRC system is only partially designed. 

Ah, ok.

> Subsystems need to be
> fully designed before they get merged.

True.
 
> For example 36-40K and 56K IR signals are both in use. It is a simple
> matter to design a receiver (or buy two receivers)  that would support
> both these frequencies. But the current LIRC model only supports  a
> single IR receiver. Adjusting it to support two receivers is going to
> break the ABI.
> 
> My choice would be to just tell the person with the 56K remote to just
> buy a new 38K remote, but other people are against that choice. That
> forces us into designing a system that can handle multiple receivers.
> There is a parallel problem with baseband encoded IR signals.
> 
> We need to think about all of these use cases before designing the
> ABI.  Only after we think we have a good ABI design should code start
> being merged. Of course we may make mistakes and have to fix the ABI,
> but there is nothing to be gained by merging the existing ABI if we
> already know it has problems.

I have here machines with 3 or 4 IR receivers (well, in a matter of fact,
I don't use all of them at the same time). Nothing stops someone to
use all IR receivers at the same. 

I've seen some interesting applications developed for students, where just
one computer running Linux is splitted into 4 different consoles. Nothing
stops that, on such usages, you may have 4 different IR transceivers working
at the same time.

In order to keep supporting the in-kernel drivers, we should create one lirc
device per each IR transceiver.

Cheers,
Mauro.

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