DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:in-reply-to:references:date:message-id:subject:from:to
         :cc:content-type:content-transfer-encoding;
        b=JXyDk/kKGQzpEi7TV2hzIxHNlzUtuCOMtxXd6lVcPVbZsK8f0LLcmG5eS9bXwqe1Lv
         cvNBedxPUd24+eT8d3lnypjYu2ljHIGLI7oUiEbo6WmwkyKF1qLwgJ7CufJwNdtP0i2M
         dMfQCETCW7W+JjrhwdddMPUtpgALE1Y4xOllw=
MIME-Version: 1.0
In-Reply-To: <4B1E5FAF.40201@redhat.com>
References: <BDRae8rZjFB@christoph> <1259264614.1781.47.camel@localhost>
	 <6B4C84CD-F146-4B8B-A8BB-9963E0BA4C47@wilsonet.com>
	 <1260240142.3086.14.camel@palomino.walls.org>
	 <20091208042210.GA11147@core.coreip.homeip.net>
	 <1260275743.3094.6.camel@palomino.walls.org>
	 <9e4733910912080452p42efa794mb7fd608fa4fbad7c@mail.gmail.com>
	 <4B1E5746.7010305@redhat.com>
	 <9e4733910912080601s1a814720qd909e47ac09f91fc@mail.gmail.com>
	 <4B1E5FAF.40201@redhat.com>
Date: Tue, 8 Dec 2009 09:31:57 -0500
Message-ID: <9e4733910912080631r6fd306c5tdfd56482583b9bf5@mail.gmail.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
From: Jon Smirl <jonsmirl@gmail.com>
To: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Andy Walls <awalls@radix.net>, Dmitry Torokhov <dmitry.torokhov@gmail.com>,
       Jarod Wilson <jarod@wilsonet.com>, Krzysztof Halasa <khc@pm.waw.pl>,
       Christoph Bartelmus <lirc@bartelmus.de>, j@jannau.net, jarod@redhat.com,
       linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
       linux-media@vger.kernel.org, superm1@ubuntu.com
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 4438
Lines: 95

On Tue, Dec 8, 2009 at 9:16 AM, Mauro Carvalho Chehab
<mchehab@redhat.com> wrote:
> Jon Smirl wrote:
>> On Tue, Dec 8, 2009 at 8:40 AM, Mauro Carvalho Chehab
>> <mchehab@redhat.com> wrote:
>>> Jon Smirl wrote:
>>>> On Tue, Dec 8, 2009 at 7:35 AM, Andy Walls <awalls@radix.net> 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.)
>>>>>
>>>>>
>>>>>> ?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.
>>>> I agree that creating devices on the fly has problems. Another
>>>> solution is to create one device for each map that is loaded. There
>>>> would be a couple built-in maps for bundled remotes - each would
>>>> create a device. Then the user could load more maps with each map
>>>> creating a device.
>>> No, please. We currently have already 89 different keymaps in-kernel. Creating
>>> 89 different interfaces per IR receiver is not useful at all.
>>>
>>> IMO, the interfaces should be created as the keymaps are associated
>>> to an specific IR receiver.
>>
>> Each IR receiver device driver would have a built-in keymap for the
>> remote bundled with it. When you load the driver it will poke the
>> input system and install the map. Any additional keymaps would get
>> loaded from user space. You would load one keymap per input device.
>>
>> You might have 89 maps in the kernel with each map being built into
>> the device driver for those 89 IR receivers. But you'll only own one
>> or two of those devices so only one or two of the 89 maps will load.
>> Building the map for the bundled receiver into the device driver is an
>> important part of achieving "just works".
>>
>> I suspect we'll have a 1,000 maps defined after ten years, most of
>> these maps will be loaded from user space. But you'll only have two or
>> three loaded at any one time into your kernel. You need one map per
>> input device created. These maps are tiny, less than 1KB.
>>
>> Having all of these maps is the price of allowing everyone to use any
>> more that they please. If you force the use of universal remotes most
>> of the maps can be eliminated.
>
> Makes sense. Yet, I would add an option at Kbuild to create a module or not
> with the bundled IR keymaps.
>
> So, it should be possible to have all of them completely on userspace or
> having them at kernelspace.

Removing the maps for the bundled remotes from the receiver device
drivers will break "just works". The map will be in an __init section
of the IR device driver. When it is fed into the input system a RAM
based structure will be created. If you really want the 1KB memory
back, use sysfs to remove the default map.  An embedded system will
have a bundled remote so it is going to want the map. If you want to
change the default map loading a new map will release the memory from
the previous map.

>
> Cheers,
> Mauro.
>


-- 
Jon Smirl
jonsmirl@gmail.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/