linux-kernel - Re: [RFC v2] Another approach to IR

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Date:	Thu, 03 Dec 2009 08:00:45 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Andy Walls <awalls@...ix.net>
CC:	Jarod Wilson <jarod@...sonet.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Devin Heitmueller <dheitmueller@...nellabs.com>,
	Jon Smirl <jonsmirl@...il.com>,
	Maxim Levitsky <maximlevitsky@...il.com>, j@...nau.net,
	jarod@...hat.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

Andy Walls wrote:
> On Wed, 2009-12-02 at 14:55 -0500, Jarod Wilson wrote:
>> On Dec 2, 2009, at 2:33 PM, Mauro Carvalho Chehab wrote:
>>
>>> Dmitry Torokhov wrote:
>> ...
>>>>>> (for each remote/substream that they can recognize).
>>>>> I'm assuming that, by remote, you're referring to a remote receiver (and not to 
>>>>> the remote itself), right?
>>>> If we could separate by remote transmitter that would be the best I
>>>> think, but I understand that it is rarely possible?
>>> IMHO, the better is to use a separate interface for the IR transmitters,
>>> on the devices that support this feature. There are only a few devices
>>> I'm aware of that are able to transmit IR codes.
>> If I'm thinking clearly, there are only three lirc kernel drivers that
>> support transmit, lirc_mceusb, lirc_zilog and lirc_serial. The mceusb
>> driver was posted, so I won't rehash what it is here. The zilog driver
>> binds to a Zilog z80 microprocessor thingy (iirc) exposed via i2c,
>> found on many Hauppauge v4l/dvb devices (PVR-150, HVR-1600, HD-PVR,
>> etc). The serial driver is fairly self-explanatory as well.
>>
>> There are also a few userspace-driven devices that do transmit, but
>> I'm assuming they're (currently) irrelevant to this discussion.
> 
> 
> I've got the CX23888 integrated IR Rx done and Tx nearly done.  I was
> waiting to see how kfifo and lirc_dev panned out before making the
> interface to userspace.
> 
> The CX23885, CX23418, and CX2584x integrated IR is essentially the same.
> I hope to have CX23885 IR done by Christmas.
> 
> Both of those IR devices are/will be encapsulated in a v4l2_subdevice
> object internally.  I was going to write lirc_v4l glue between the
> v4l2_device/v4l2_subdev_ir_ops and lirc_dev.
> 
> As for the the I2C chips, I was going to go back and encapsulate those
> in the v4l2_subdevice object as well, so then my notional lirc_v4l could
> pick those up too.  The I2C subsystem only allows one binding to an I2C
> client address/name on a bus.  So without some new glue like a notional
> lirc_v4l, it *may* be hard to share between ir-kbd-i2c and lirc_i2c and
> lirc_zilog.

Maybe you're having a bad time because you may be trying to integrate lirc
at the wrong place.

All devices at V4L tree including ir-kbd-i2c use ir-common.ko 
(at /drivers/media/common tree) module to communicate to IR's. 
I'm preparing some patches to extend this also to dvb-usb devices 
(that uses a close enough infrastructure). 

Also, most of the decoding code are there, in a form of helper routines.

As the idea is to provide lirc interface to all devices that can work with
raw pulse/space, the proper place is to write a subroutine there that, once
called, will make those pulse/space raw codes available to lirc and will
call the needed decoders to export them also to evdev.

The code at ir-common module was originally built to be used by V4L, but I'm
porting the code there to be generic enough to be a library that can be used
by other drivers. So, lirc_zilog and other lirc devices that will need to open
evdev interfaces after running a decoder can use them.

Due to that, we shouldn't add v4l2_subdevice there. Nothing prevents to create
a v4l2-ir-subdev glue if you want to see the IR's as subdevices, but this should
be implemented as a separate module.

Cheers,
Mauro.
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