Date:	Wed, 2 Dec 2009 10:37:02 -0500
From:	Jon Smirl <jonsmirl@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Devin Heitmueller <dheitmueller@...nellabs.com>,
	Maxim Levitsky <maximlevitsky@...il.com>, awalls@...ix.net,
	j@...nau.net, jarod@...hat.com, jarod@...sonet.com, khc@...waw.pl,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, lirc-list@...ts.sourceforge.net,
	superm1@...ntu.com, Christoph Bartelmus <lirc@...telmus.de>
Subject: Re: [RFC v2] Another approach to IR

On Wed, Dec 2, 2009 at 4:38 AM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Tue, Dec 01, 2009 at 07:05:49PM -0200, Mauro Carvalho Chehab wrote:
>> Dmitry Torokhov wrote:
>> > On Tue, Dec 01, 2009 at 05:00:40PM -0200, Mauro Carvalho Chehab wrote:
>> >> Dmitry Torokhov wrote:
>> >>> On Tue, Dec 01, 2009 at 03:29:44PM -0200, Mauro Carvalho Chehab wrote:
>> >>>> For sure we need to add an EVIOSETPROTO ioctl to allow the driver
>> >>>> to change the protocol in runtime.
>> >>>>
>> >>> Mauro,
>> >>>
>> >>> I think this kind of confuguration belongs to lirc device space,
>> >>> not input/evdev. This is the same as protocol selection for psmouse
>> >>> module: while it is normally auto-detected we have sysfs attribute to
>> >>> force one or another and it is tied to serio device, not input
>> >>> device.
>> >> Dmitry,
>> >>
>> >> This has nothing to do with the raw interface nor with lirc. This problem
>> >> happens with the evdev interface and already affects the in-kernel drivers.
>> >>
>> >> In this case, psmouse is not a good example. With a mouse, when a movement
>> >> occurs, you'll receive some data from its port. So, a software can autodetect
>> >> the protocol. The same principle can be used also with a raw pulse/space
>> >> interface, where software can autodetect the protocol.
>> >
>> > Or, in certain cases, it can not.
>> >
>> > [... skipped rationale for adding a way to control protocol (with which
>> > I agree) ...]
>> >
>> >> To solve this, we really need to extend evdev API to do 3 things: enumberate the
>> >> supported protocols, get the current protocol(s), and select the protocol(s) that
>> >> will be used by a newer table.
>> >>
>> >
>> > And here we start disagreeing. My preference would be for adding this
>> > API on lirc device level (i.e. /syc/class/lirc/lircX/blah namespace),
>> > since it only applicable to IR, not to input devices in general.
>> >
>> > Once you selected proper protocol(s) and maybe instantiated several
>> > input devices then udev (by examining input device capabilities and
>> > optionally looking up at the parent device properties) would use
>> > input evdev API to load proper keymap. Because translation of
>> > driver-specific codes into standard key definitions is in the input
>> > realm. Reading these driver-specific codes from hardware is outside of
>> > input layer domain.
>> >
>> > Just as psmouse ability to specify protocol is not shoved into evdev;
>> > just as atkbd quirks (force release key list and other driver-specific
>> > options) are not in evdev either; we should not overload evdev interface
>> > with IR-specific items.
>>
>> I'm not against mapping those features as sysfs atributes, but they don't belong
>> to lirc, as far as I understand. From all we've discussed, we'll create a lirc
>> interface to allow the direct usage of raw IO. However, IR protocol is a property
>> that is not related to raw IO mode but, instead, to evdev mode.
>>
>
> Why would protocol relate to evdev node? Evdev does not really care what
> how the fact that a certain button was pressed was communicated to it.
> It may be deliveretd through PS/2 port, or maybe it was Bluetooth HID,
> or USB HID or USB boot protocol or some custom protocol, or RC-5, NEC or
> some custom IR protocol. It makes no difference _whatsoever_ to evdev
> nor any users of evdev care about protocol used by underlying hardware
> device to transmit the data.
>
>> We might add a /sys/class/IR and add IR specific stuff there, but it seems
>> overkill to me and will hide the fact that those parameters are part of the evdev
>> interface.
>>
>> So, I would just add the IR sysfs parameters at the /sys/class/input, if
>> the device is an IR (or create it is /sys/class/input/IR).
>>
>> I agree that the code to implement the IR specific sysfs parameter should be kept
>> oustide input core, as they're specific to IR implementations.
>>
>> Would this work for you?
>
> I am seeing a little bit differently structured subsystem for IR at the
> moment. I think we should do something like this:
>
> - receivers create /sys/class/lirc devices. These devices provide API
>  with a ring buffer (fifo) for the raw data stream coming from (and to)
>  them.

The FIFO will have to appear as a /dev/device or be in debugfs. GregKH
sent earlier mail telling me to get the FIFO out of sysfs.

> - we allow registering several data interfaces/decoders that can be bound
>  (manually or maybe automatically) to lirc devices. lirc devices may
>  provide hints as to which interface(s) better suited for handling the
>  data coming form particular receiver. Several interfaces may be bound
>  to one device at a time.
> - one of the interfaces is interface implementing current lirc_dev
> - other interfaces may be in-kernel RC-5 decoder or other decoders.
>  decoders will create instances of input devices (for each
>  remote/substream that they can recognize).

This includes defining IR events for evdev with vendor/device/command triplets?
You need those standard events to make apps IR aware.

LIRC will also need to inject those events after decoding pulse data.

>
> This way there is clear layering, protocol selection is kept at lirc
> level.

Did you checkout capabilities bits in evdev?

>
> Would this work?
>
> --
> Dmitry
>



-- 
Jon Smirl
jonsmirl@...il.com
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