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Date: Thu, 3 Dec 2009 00:08:13 -0500
Message-ID: <9e4733910912022108j71d0c27fh75dacfa79dca7c22@mail.gmail.com>
Subject: Re: [RFC v2] Another approach to IR
From: Jon Smirl <jonsmirl@gmail.com>
To: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Jarod Wilson <jarod@wilsonet.com>,
       Dmitry Torokhov <dmitry.torokhov@gmail.com>,
       Jarod Wilson <jarod@redhat.com>,
       Devin Heitmueller <dheitmueller@kernellabs.com>,
       Maxim Levitsky <maximlevitsky@gmail.com>, awalls@radix.net,
       j@jannau.net, khc@pm.waw.pl, linux-input@vger.kernel.org,
       linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
       lirc-list@lists.sourceforge.net, superm1@ubuntu.com,
       Christoph Bartelmus <lirc@bartelmus.de>
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On Wed, Dec 2, 2009 at 9:22 PM, Mauro Carvalho Chehab
<mchehab@redhat.com> wrote:
> Jon Smirl wrote:
>> On Wed, Dec 2, 2009 at 3:04 PM, Jarod Wilson <jarod@wilsonet.com> wrote:
>>> On Dec 2, 2009, at 2:56 PM, Dmitry Torokhov wrote:
>>>
>>>> On Wed, Dec 02, 2009 at 02:22:18PM -0500, Jarod Wilson wrote:
>>>>> On 12/2/09 12:30 PM, Jon Smirl wrote:
>>>>>>>>> (for each remote/substream that they can recognize).
>>>>>>>>>> I'm assuming that, by remote, you're referring to a remote receiver (and not to
>>>>>>>>>> the remote itself), right?
>>>>>>>> If we could separate by remote transmitter that would be the best I
>>>>>>>> think, but I understand that it is rarely possible?
>>>>>> The code I posted using configfs did that. Instead of making apps IR
>>>>>> aware it mapped the vendor/device/command triplets into standard Linux
>>>>>> keycodes. ?Each remote was its own evdev device.
>>>>> Note, of course, that you can only do that iff each remote uses distinct
>>>>> triplets. A good portion of mythtv users use a universal of some sort,
>>>>> programmed to emulate another remote, such as the mce remote bundled
>>>>> with mceusb transceivers, or the imon remote bundled with most imon
>>>>> receivers. I do just that myself.
>>>>>
>>>>> Personally, I've always considered the driver/interface to be the
>>>>> receiver, not the remote. The lirc drivers operate at the receiver
>>>>> level, anyway, and the distinction between different remotes is made by
>>>>> the lirc daemon.
>>>> The fact that lirc does it this way does not necessarily mean it is the
>>>> most corerct way.
>>> No, I know that, I'm just saying that's how I've always looked at it, and that's how lirc does it right now, not that it must be that way.
>>>
>>>> Do you expect all bluetooth input devices be presented
>>>> as a single blob just because they happen to talk to the sane receiver
>>>> in yoru laptop? Do you expect your USB mouse and keyboard be merged
>>>> together just because they end up being serviced by the same host
>>>> controller? If not why remotes should be any different?
>>> A bluetooth remote has a specific device ID that the receiver has to pair with. Your usb mouse and keyboard each have specific device IDs. A usb IR *receiver* has a specific device ID, the remotes do not. So there's the major difference from your examples.
>>
>> Actually remotes do have an ID. They all transmit vendor/device pairs
>> which is exactly how USB works.
>>
>
> Well, the description of NEC and RC5 protocol at http://www.sbprojects.com/knowledge/ir/rc5.htm
> doesn't mention any vendor/device pair, nor I'm able to get them with the IR hardware decoders
> I have.

Some of the protocols were not intended to be multi-vendor  - the
vendor is implicit in the protocol encoding. You don't have to split
the IR codes into vendor/device/command triplets. I just do that
because it is convenient to think of them that way. It is equally
valid to treat them as a 64b integers and use four bits of the int to
encode the protocol.  It should really be a quad
protocol/vendor/device/command and some of the fields may be missing.
Bottom line, you are looking for unique codes how the fields are split
up doesn't really matter.

A fixed protocol receiver is more of a challenge. You have to figure
out how to make a universal remote transmit device codes for a device
you don't already own that is also encoded in the protocol your
hardware supports. There's nothing we can do about that problem in
Linux, its a side effect of fixed protocol decode hardware. You're
just going to have to start guessing devices in the remote until you
find one that uses your fixed protocol and doesn't also activate the
devices you own. We can put suggestions in the doc when working
devices are discovered. With a universal receiver the problem is
simpler, just pick a device you don't own - the encoding protocol
doesn't matter. These are generic problems with IR that are the same
no matter how things get implemented in Linux.


-- 
Jon Smirl
jonsmirl@gmail.com
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