IR remote control autorepeat / evdev

Mauro Carvalho Chehab mchehab at
Wed May 11 18:10:03 PDT 2011

Em 12-05-2011 02:37, Anssi Hannula escreveu:
> On 12.05.2011 02:52, Mauro Carvalho Chehab wrote:
>> Em 11-05-2011 19:59, Anssi Hannula escreveu:
>>>> No. It actually depends on what driver you're using. For example, for most dvb-usb
>>>> devices, this is given by the logic bellow:
>>>> 	if (d->props.rc.legacy.rc_interval < 40)
>>>> 		d->props.rc.legacy.rc_interval = 100; /* default */
>>>> 	input_dev->rep[REP_PERIOD] = d->props.rc.legacy.rc_interval;
>>>> 	input_dev->rep[REP_DELAY]  = d->props.rc.legacy.rc_interval + 150;
>>>> where the rc_interval defined by device entry at the dvb usb drivers.
>>> Isn't that function only called for DVB_RC_LEGACY mode?
>> I just picked one random piece of the code that covers several RC remotes (most
>> dvb-usb drivers are still using the legacy mode). Similar code are there for
>> other devices.
> I don't see any other places:
> $ git grep 'REP_PERIOD' .
> dvb/dvb-usb/dvb-usb-remote.c:   input_dev->rep[REP_PERIOD] =
> d->props.rc.legacy.rc_interval;

Indeed, the REP_PERIOD is not adjusted on other drivers. I agree that we
should change it to something like 125ms, for example, as 33ms is too 
short, as it takes up to 114ms for a repeat event to arrive.

The REP_PERIOD is adjusted, however, on several drivers. Also, RC core changes
its default to 500ms, to avoid ghost keystrokes:
	dev->input_dev->rep[REP_DELAY] = 500;

>>> Maybe I wasn't clear, but I'm talking only about the devices handled by
>>> rc-core.
>> With just a few exceptions, the repeat period/delay that were there before
>> porting to rc-core were maintained. There are space for adjustments, as we
>> did on a few cases.
> The above is the only place where the repeat period is set in the
> drivers/media tree, and it is not an rc-core device. Other devices
> therefore use the 33ms kernel default.
> Maybe I am missing something?
>> Em 11-05-2011 22:53, Dmitry Torokhov escreveu:
>>> On Wed, May 11, 2011 at 08:59:16PM +0300, Anssi Hannula wrote:
>>>> I meant replacing the softrepeat with native repeat for such devices
>>>> that have native repeats but no native release events:
>>>> - keypress from device => keydown + keyup
>>>> - repeat from device => keydown + keyup
>>>> - repeat from device => keydown + keyup
>>>> This is what e.g. ati_remote driver now does.
>>>> Or alternatively
>>>> - keypress from device => keydown
>>>> - repeat from device => repeat
>>>> - repeat from device => repeat
>>>> - nothing for 250ms => keyup
>>>> (doing it this way requires some extra handling in X server to stop its
>>>> softrepeat from triggering, though, as previously noted)
>>>> With either of these, if one holds down volumeup, the repeat works, and
>>>> stops volumeup'ing immediately when user releases the button (as it is
>>>> supposed to).
>>> Unfortunately this does not work for devices that do not have hardware
>>> autorepeat and also stops users from adjusting autorepeat parameters to
>>> their liking.
>> Yes. A solution like the above would limit the usage. There are some remotes
>> (like for example, the Hauppauge Grey remotes I have here) that a simple
>> keypress generates, in general, up to 3 scancodes (the normal keypress and
>> up to two "bounced" repeat keycodes). So, the software key delay also serves
>> as a way to de-bounce the keypress.
> I probably forgot to mention it, but I'm not suggesting removal of the
> repetition delay (500ms), it can stay for this reason exactly.
>>> It appears that the delay to check whether the key has been released is
>>> too long (almost order of magnitude longer than our typical autorepeat
>>> period).
>> Yes, because, for example, with NEC and RC-5 protocols, one keystroke or one
>> repeat event takes 110/114 ms to be transmitted. The delay actually varies 
>> from protocol to protocol, so it is possible to do some adjustments, based on
>> the protocol type, but it is an order of magnitude longer than a keyboard or
>> mouse.
>>> I think we should increase the period for remotes (both in
>>> kernel and in X, and also see if the release check delay can be made
>>> shorter, like 50-100 ms.
>> Some adjustments like that can be made, but they are device-driver specific.
>> For example, some in-hardware IR decoders with KS007 micro-controller just
>> removes all repeat keycodes and replace them with new keystrokes. There are
>> some shipped remotes that don't support the RC-5 or NEC key repeat event. So,
>> on those, if you keep a key pressed, you just receive the same scancode several
>> times.
>> The last time I double checked all remotes I have here, on all cases the auto-repeat
>> logic were doing the right job, but I won't doubt that we need to add some additional
>> adjustments for some boards/devices.
> Does "doing the right job" mean that you are getting zero repeat (2)
> events after releasing a remote button?

I mean that the logic is ok. The timings may be not. The timings were not
touched when we've ported the already supported IR's to the rc-core, except
when we noticed some troubles with them.

> Because that is what I expect to happen, and that is what e.g. LIRC
> (which most people seem to still use with HTPC software - like XBMC
> which I'm a developer of) does.

That's what we all expect to happen.

>> Anssi, what's the hardware that you're using?
> I'm using ati_remote ported to rc-core (don't know yet if it makes any
> sense, though).
> However, as noted, reading ir-main.c I fail to see why this wouldn't
> happen with all rc-core devices, as all devices seem to use same
> IR_KEYPRESS_TIMEOUT and REP_PERIOD (though you seem to suggest otherwise
> above, maybe you can show me wrong? :) ).

They share the same logic, but hardware decoders behave different than
software ones.


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