linux-kernel - Re: [patch 0/2] Winbond IR Driver

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Date:	Sun, 16 Aug 2009 20:43:50 +0200
From:	David Härdeman <david@...deman.nu>
To:	Maxim Levitsky <maximlevitsky@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
	jbarnes@...tuousgeek.org, akpm@...ux-foundation.org,
	dmitry.torokhov@...il.com
Subject: Re: [patch 0/2] Winbond IR Driver - v2

On Sun, Aug 16, 2009 at 01:10:11AM +0300, Maxim Levitsky wrote:
>On Sat, 2009-08-15 at 22:10 +0200, David Härdeman wrote:
>> On Sat, Aug 15, 2009 at 06:02:27AM +0300, Maxim Levitsky wrote:
>>>
>>> Then why not to implement lirc driver?
>>
>> That's a fair question, but I'm afraid you're putting the cart before
>> the horse.
>
>No, I just want to write the driver that fully exposes the hardware. I
>don't care if it has to be outside or not.

That's not a very user-friendly sentiment. The entire idea is to extend 
the input subsystem so that it fully exposes the hardware *and* gives 
users the benefit of in-kernel drivers.

>> The question is not why anyone would want to write an in-kernel driver
>> but rather why anyone would want to write an out-of-kernel driver.
>>
>> There have been repeated attempts to get LIRC merged with the kernel,
>> and the feedback has been pretty consistent - make it part of the input
>> subsystem.
>>
>> I have written the driver for theo input system and it limits the driver
>> somewhat. I am working on extending the input system to accomodate IR
>> drivers (see the discussion of EV_IR on the linux-input list).
>
>The EV_IR thing is that he attempts to put all IR decoding in kernel,
>and on top of that create a configfs config system.

I never proposed a configfs system. I only proposed a part of Jon 
Smirl's EV_IR functionality. I think the configfs system as well as the 
in-kernel protocol _en_coders are overengineering.

>I first thought it would be nice, but then realized that this is really
>bad idea.
>Currently LIRC has very oiled system for decoding pretty much every
>remote that exist. It can cope with all kind of troubles, including not
>very accurate receivers.

I think you've misunderstood my EV_IR suggestion on the linux-input 
list. Part of that proposal is to allow drivers to generate IR_RAW 
timing events (if asked to do so via an ioctl), then you could continue 
to use lirc with some minimal changes to the lirc daemon while still 
getting the benefits of in-kernel drivers. I have a hard time seeing 
what would be wrong with that? Whether the input subsystem *also* 
includes (optional) IR decoding or not should not matter to lirc fans as 
long as it includes some kind of IR_RAW support (which it does both in 
Jon's proposal and in mine).

>On top of that there are pure userspace devices, like a IR diode
>connected to soundcard. It would be nice to do all the raw signal
>decoding in one place. Once signal is decoded, lirc forwards the input
>signal to the kernel via uinput, so it is a part of input system.

That's a red herring, there is always going to be esoteric DIY hardware, 
and no matter which API is used in the kernel, that hardware can always 
use user-space drivers.

>The way kernel hands in the raw IR data to lirc doesn't matter much. It
>is really just a queue of numbers. It can be forced into input system,
>but there is really no need for that.

There really is a need if you want in-kernel drivers.

>> Feel free to help me out in implementing that API, and porting LIRC
>> drivers, and all the benefits of in-kernel drivers will flow from that
>> work.
>
>This isn't a bad idea.

Good, we agree on this point, which is the most important one. IR_RAW 
should be enough for the lirc daemon, right? So let's make sure 
something like that gets added to the input subsystem and we can take it 
from there...

>>>This driver as I understand is a driver for single remote shipped with
>>>the notebook.
>>
>> It's a driver for a winbond chipset shipped with many Intel desktop
>> "media" motherboards (DP35DP, DG33TL, DX388T, DX488T2, DP455G, DG45ID
>> and DG45FC are the ones I'm aware of).
>
>But it won't work with my JVC remote?....

Not sure what you JVC remote has to do with the Intel mainboards that 
include the WPCD376I chipset.

Anyway, based on past experience of JVC remotes I'm guessing that your 
remote uses some version of the NEC protocol, in that case it will be 
supported...and IR_RAW (or something similar) will be supported if it is 
accepted by the input subsystem maintainers so you will additionally be 
able to use that air conditioning remote which implements a completely 
wonky IR protocol together with lirc - if you want to...

Regards,
David Härdeman

(trimmed some people of the CC list which are unlikely to be interested 
in this discussion, I hope Dmitry will speak up soon).

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