Re: [RFC] What are the goals for the architecture of an in-kernel IR system?

Dmitry Torokhov
2009-12-03T17:55:33Z

On Thu, Dec 03, 2009 at 01:09:14PM +0100, Gerd Hoffmann wrote:
> On 12/03/09 05:29, Jarod Wilson wrote:
>> On Dec 1, 2009, at 10:28 AM, Gerd Hoffmann wrote:
>>
>>>> Anyway, we shouldn't postpone lirc drivers addition due to that.
>>>> There are still lots of work to do before we'll be able to split
>>>> the tables from the kernel drivers.
>>>
>>> Indeed. The sysfs bits are future work for both lirc and evdev
>>> drivers. There is no reason to make the lirc merge wait for it.
>>
>> At this point, my plan is to try to finish cleaning up lirc_dev and
>> lirc_mceusb at least over the weekend while at FUDCon up in Toronto,
>> and resubmit them next week.
>
> Good plan IMHO. Having lirc_dev merged quickly allows in-kernel drivers
> start supporting lirc.

No, please, wait just a minute. I know it is tempting to just merge
lirc_dev and start working, but can we first agree on the overall
subsystem structure before doing so. It is still quite inclear to me.

The open questions (for me at least):

- do we create a new class infrastructure for all receivers or only for
ones plugged into lirc_dev? Remember that classifying objects affects
how udev and friemds see them and may either help or hurt writing PnP
rules.

- do we intend to support in-kernel sotfware decoders? What is the
structure? Do we organize them as a module to be used by driver
directly or the driver "streams" the data to IR core and the core
applies decoders (in the same fashion input events from drivers flow
into input core and then distributed to all bound interfaces for
processing/conversion/transmission to userspace)?

- how do we control which decoder should handle particular
receiver/remote? Is it driver's decision, decoder's decision, user's
or all of the above?

- do we allow to have several decorers active at once for a receiver?

- who decides that we want to utilize lirc_dev? Driver's themselves, IR
core (looking at the driver/device "capabilities"), something else?

- do we recognize and create input devices "on-fly" or require user
intervention? Semantics for splitting into several input/event
devices?

Could anyone please draw me a picture, starting with a "receiver"
piece of hardware. I am not concerned much with how exactly receiver is
plugged into a particular subsystem (DVB/V4L etc) since it would be
_their_ implementation detail, but with the flow in/out of that
"receiver" device.

Now as far as input core goes I see very limited number of changes that
may be needed:

- Allow to extend size of "scancode" in EVIOC{S,G}KEYCODE if we are
unable to limit ourselves to 32 bits (keeping compatibility of course)

- Maybe adding new ioctl to "zap" the keymap table

- Adding more key EV_KEY/KEY_* definitons, if needed

Thanks.

--
Dmitry