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

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Date:	Thu, 26 Nov 2009 17:08:40 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Krzysztof Halasa <khc@...waw.pl>
CC:	Jarod Wilson <jarod@...hat.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-kernel@...r.kernel.org,
	Mario Limonciello <superm1@...ntu.com>,
	linux-input@...r.kernel.org, linux-media@...r.kernel.org,
	Janne Grunau <j@...nau.net>,
	Christoph Bartelmus <lirc@...telmus.de>
Subject: Re: [RFC] Should we create a raw input interface for IR's ? - Was:
 Re: [PATCH 1/3 v2] lirc core device driver infrastructure

Krzysztof Halasa wrote:
> Mauro Carvalho Chehab <mchehab@...hat.com> writes:
> 
>> The issue I see is to support at the same time NEC and RC5 protocols. While
>> this may work with some devices, for others, the hardware won't allow.
> 
> Sure. We can handle it for the "simple" devices at least.
> 
>>> I think the mapping should be: key = proto + group + raw code, while
>>> key2 could be different_proto + different group (if any) + another code.
>> This may work for protocols up to RC5, that uses either 8 or 16 bits.
>> However, RC6 mode 6 codes can be 32 bits, and we have "only" 32 bits
>> for a scancode. So, we don't have spare bits to represent a protocol, 
>> if we consider RC6 mode 6 codes as well.
> 
> I don't see this limitation. The number of bits should depend on the
> protocol.

see include/linux/input.h:

struct input_event {
        struct timeval time;
        __u16 type;
        __u16 code;
        __s32 value;
};

extending the value to more than 32 bits require some changes at the input layer,
probably breaking kernel API.

> 
>> See above. Also, several protocols have a way to check if a keystroke were
>> properly received. When handling just one protocol, we can use this to double
>> check the key. However, on a multiprotocol mode, we'll need to disable this
>> feature.
> 
> I don't think so. We can pass the space/mark data to all (configured,
> i.e. with active mapping) protocol handlers at once. Should a check
> fail, we ignore the data. Perhaps another protocol will make some sense
> out of it.

What happens if it succeeds on two protocol handlers?

Cheers,
Mauro.
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