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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Message-ID: <4B0ACB70.9090707@redhat.com>
Date:	Mon, 23 Nov 2009 15:50:40 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	James Mastros <james@...tros.biz>
CC:	Devin Heitmueller <dheitmueller@...nellabs.com>,
	Krzysztof Halasa <khc@...waw.pl>,
	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

James Mastros wrote:
> 2009/11/23 Devin Heitmueller <dheitmueller@...nellabs.com>:
>> Just bear in mind that with the current in-kernel code, users do *not
>> * have to manually select the RC code to use if they are using the
>> default remote that shipped with the product.
> This could still happen, if LIRC checks the identifiers of the
> reciving device, and has a database that tells it mappings between
> those devices and the remote controls that shipped with them.

True, but this means that everyone with an IR will need to use lirc.

/me thinks that, whatever decided with those lirc drivers, this should be applied also to the existing V4L/DVB drivers.

IMO, it would be better to load the tables at the boot time (or at the 
corresponding hotplug event, for USB devices).

> However, it occours to me that the IR circumstances map pretty well to
> what happens with ps/2 and serial devices now:
> 
> 1: There are a variety of drivers for serio computer-side hardware,
> each of which speaks the serio interface to the next-higher level.
> These corrospond to the drivers for IR recievers.
> 2: There's a raw serio interface, for those wishing to do strange things.
> 3: There's also a variety of things that take data, using the kernel
> serio API, and decode it into input events -- the ps2 keyboard driver,
> the basic mouse driver, the advanced mice drivers. 

Seems an interesting model.

> This is where the
> interface falls down a little bit -- the ps2 keyboard driver is the
> closest analogue to what I'm suggesting.  The ps2 keyboard driver
> creates scancode events, which map nicely to what the keyboard is
> sending -- these are, for ex, rc5 codes.  It will also produce
> key-up/key-down events, if it has a keymap loaded.  (This is the
> difference with a ps2 keyboard -- a ps2 keyboard gets a map assigned
> to it at boottime, so it works out-of-box.  This isn't really possible
> with an IR remote -- though perhaps rc5 is standarized enough, I don't
> think other protocols neccessarly are.)

Even with RC5, there are some vendors that implement it differently on his
IR (for example, using VCR and/or TV group for the keys).

> Userspace would have to load a keymap; those don't really belong in
> kernel code.  Of course, userspace could look at the device
> identifiers to pick a reasonable default keymap if it's not configured
> to load another, solving the out-of-box experince.

I like this idea. We currently have hundreds of IR keymaps already in kernel.
It seems good to remove from kernel and let udev load those.

Cheers,
Mauro.
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