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Subject: Re: IR raw input is not sutable for input system
From: Maxim Levitsky <maximlevitsky@gmail.com>
To: Trent Piepho <xyzzy@speakeasy.org>
Cc: Jarod Wilson <jarod@wilsonet.com>,
       Dmitry Torokhov <dmitry.torokhov@gmail.com>,
       Krzysztof Halasa <khc@pm.waw.pl>,
       Mauro Carvalho Chehab <mchehab@redhat.com>,
       Jarod Wilson <jarod@redhat.com>, linux-kernel@vger.kernel.org,
       Mario Limonciello <superm1@ubuntu.com>, linux-input@vger.kernel.org,
       linux-media@vger.kernel.org, Janne Grunau <j@jannau.net>,
       Christoph Bartelmus <lirc@bartelmus.de>
In-Reply-To: <Pine.LNX.4.58.0911241918390.30284@shell2.speakeasy.net>
References: <200910200956.33391.jarod@redhat.com>
	 <200910200958.50574.jarod@redhat.com> <4B0A765F.7010204@redhat.com>
	 <4B0A81BF.4090203@redhat.com> <m36391tjj3.fsf@intrepid.localdomain>
	 <20091123173726.GE17813@core.coreip.homeip.net>
	 <4B0B6321.3050001@wilsonet.com> <1259105571.28219.20.camel@maxim-laptop>
	 <Pine.LNX.4.58.0911241918390.30284@shell2.speakeasy.net>
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Date: Wed, 25 Nov 2009 15:28:54 +0200
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On Tue, 2009-11-24 at 19:32 -0800, Trent Piepho wrote: 
> On Wed, 25 Nov 2009, Maxim Levitsky wrote:
> >
> > Its not the case.
> > There are many protocols, I know that by experimenting with my universal
> > remote. There are many receivers, and all have different accuracy.
> > Most remotes aren't designed to be used with PC, thus user has to invent
> > mapping between buttons and actions.
> > Its is not possible to identify remotes accurately, many remotes send
> > just a 8 bit integer that specifies the 'model' thus many remotes can
> > share it.
> 
> The signal recevied by the ir receiver contains glitches.  Depending on the
> receiver there can be quite a few.  It is also not trivial to turn the raw
> signal sent by the remote into a digital value, even if you know what to
> expect.  It takes digital signal processing techniques to turn the messy
> sequence of inaccurate mark and space lengths into a best guess at what
> digital code the remote sent.
Exactly

> 
> It's like turning raw VBI data into decoded ASCII teletext from a simulated
> keyboard device, all in the kernel.
You hit a nail on the head with this one.


> 
> > Kernel job is to take the information from device and present it to
> > userspace using uniform format, that is kernel does 1:1 translating, but
> > doesn't parse the data.

> 
> One thing that could be done, unless it has changed much since I wrote it
> 10+ years ago, is to take the mark/space protocol the ir device uses and sent
> that data to lircd via the input layer.  It would be less efficient, but
> would avoid another kernel interface.  Of course the input layer to lircd
> interface would be somewhat different than other input devices, so
> it's not entirely correct to say another interface is avoided.
I agree with this one, but it is very optional.

I also want to add that lirc can and does behave just like an input
device. 
It sends the parsed events using uinput, so your remote appears just
like a keyboard.
It can even act like a mouse, and btw I use that feature, and it works
just fine.


So lets put lirc into the kernel finally?

Best regards,
Maxim Levitsky


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