linux-kernel - Re: [RFC v2] Another approach to IR

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Message-ID: <4B16CCD7.20601@redhat.com>
Date:	Wed, 02 Dec 2009 18:23:51 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Jarod Wilson <jarod@...sonet.com>, Jarod Wilson <jarod@...hat.com>,
	Jon Smirl <jonsmirl@...il.com>,
	Devin Heitmueller <dheitmueller@...nellabs.com>,
	Maxim Levitsky <maximlevitsky@...il.com>, awalls@...ix.net,
	j@...nau.net, khc@...waw.pl, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	lirc-list@...ts.sourceforge.net, superm1@...ntu.com,
	Christoph Bartelmus <lirc@...telmus.de>
Subject: Re: [RFC v2] Another approach to IR

Dmitry Torokhov wrote:
> On Wed, Dec 02, 2009 at 03:04:30PM -0500, Jarod Wilson 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.
>>
> 
> Not exactly... I can have 2 identical USB keyboadrs form the same
> manufacturer and they will still be treated separately. BT has session
> ID to help distinguish between devices.
> 
>>> Now I understand that if 2 remotes send completely identical signals we
>>> won't be able to separete them, but in cases when we can I think we
>>> should.
>> I don't have a problem with that, if its a truly desired feature. But
>> for the most part, I don't see the point. Generally, you go from
>> having multiple remotes, one per device (where "device" is your TV,
>> amplifier, set top box, htpc, etc), to having a single universal
>> remote that controls all of those devices. But for each device (IR
>> receiver), *one* IR command set. The desire to use multiple distinct
>> remotes with a single IR receiver doesn't make sense to me. Perhaps
>> I'm just not creative enough in my use of IR. :)
> 
> Didn't Jon posted his example whith programmable remote pretending to be
> several separate remotes (depending on the mode of operation) so that
> several devices/applications can be controlled without interfering with
> each other?
> 
>From what I understood, he is using the same physical remote, but creating different
IR groups of keys on it, each group meant to be used by a different application.

For such usage, some software will need to filter the scancode group and send
them only for a certain application. This can be done easily by using lirc,
purely in userspace.

Another alternative (that will also work for multimedia keys on a keyboard) is
to add a filtering subsystem at evdev that will send certain events for just certain
PID's.

Of course, it is feasible to do it in kernel, but, IMHO, it would be better to let
userspace to take care of this.

Cheers,
Mauro.
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