Re: [RFC] Should we create a raw input interface for IR's ? - Was: Re: [PATCH 1/3 v2] lirc core device driver infrastructure

[Jon Smirl <jonsmirl@gmail.com>]

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