How to synchronize leds in trigger

How to synchronize leds in trigger

[Oleh Kravchenko]

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Hello Linux LEDs developer!

I have two GPIO LEDs one is red another is blue.
I want that LEDs is blinking in pair.

Could you please advice how to achive this behaviour:
1. Red is active for 500 ms, Blue stays off.
2. Next step is Blue is active for 500 ms, Red is stays off.
3. Goto #1

I tried standard pattern trigger, but very quickly it miss matches.

-- 
Best regards,
Oleh Kravchenko


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Re: How to synchronize leds in trigger

[Jacek Anaszewski]

Hi Oleh,

On 1/27/20 10:51 PM, Oleh Kravchenko wrote:
> Hello Linux LEDs developer!
> 
> I have two GPIO LEDs one is red another is blue.
> I want that LEDs is blinking in pair.
> 
> Could you please advice how to achive this behaviour:
> 1. Red is active for 500 ms, Blue stays off.
> 2. Next step is Blue is active for 500 ms, Red is stays off.
> 3. Goto #1
> 
> I tried standard pattern trigger, but very quickly it miss matches.

Currently LED framework does not support that.
We would need a global pattern trigger, that would allow registering
a set of LEDs for events firing at different time slots.

It is feasible, but it would take months to agree upon interface
and implementation. The question is whether it wouldn't be an overkill.
What prevents you from solving this problem in userspace?

-- 
Best regards,
Jacek Anaszewski

Re: How to synchronize leds in trigger

[Oleh Kravchenko]

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Hello Jacek,

On 28.01.20 21:58, Jacek Anaszewski wrote:
> Currently LED framework does not support that.
> We would need a global pattern trigger, that would allow registering
> a set of LEDs for events firing at different time slots.
>
> It is feasible, but it would take months to agree upon interface
> and implementation. The question is whether it wouldn't be an overkill.

I'm happy to invest my time to implement such functionality.
I think it can be really useful for LEDs array like CR0014114 <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.5&id=b9dd69155371ebd7055c182e30423edc9104239f>.

In few days I can publish my vision,
but before that could you please explain why it will took months?
Where it can be hard to implement?

> What prevents you from solving this problem in userspace?

User-space don't fast enough to provide correct timings.

-- 
Best regards,
Oleh Kravchenko



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Re: How to synchronize leds in trigger

[Marek Behun]

On Thu, 30 Jan 2020 09:57:08 +0200
Oleh Kravchenko <oleg@kaa.org.ua> wrote:

> I'm happy to invest my time to implement such functionality.
> I think it can be really useful for LEDs array like CR0014114 <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.5&id=b9dd69155371ebd7055c182e30423edc9104239f>.
> 
> In few days I can publish my vision,
> but before that could you please explain why it will took months?
> Where it can be hard to implement?
> 

Just look at how long the API for RGB LEDs is being agreed upon. It is
over a year already, if not longer, and still not merged.

> > What prevents you from solving this problem in userspace?  
> 
> User-space don't fast enough to provide correct timings.
> 

Can you provide a video or something where we can see?

Re: How to synchronize leds in trigger

[Pavel Machek]

Hi!

> > What prevents you from solving this problem in userspace?
> 
> User-space don't fast enough to provide correct timings.

That's hard to believe.

							Pavel

Re: How to synchronize leds in trigger

[Dan Murphy]

Marek

On 1/30/20 3:44 AM, Marek Behun wrote:
> On Thu, 30 Jan 2020 09:57:08 +0200
> Oleh Kravchenko <oleg@kaa.org.ua> wrote:
>
>> I'm happy to invest my time to implement such functionality.
>> I think it can be really useful for LEDs array like CR0014114 <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.5&id=b9dd69155371ebd7055c182e30423edc9104239f>.
>>
>> In few days I can publish my vision,
>> but before that could you please explain why it will took months?
>> Where it can be hard to implement?
>>
> Just look at how long the API for RGB LEDs is being agreed upon. It is
> over a year already, if not longer, and still not merged.

Agreed. The patchset for RGB LEDs has been waiting since November for 
merge or even applied to led-next.  I rebased the patches and added the 
ACKs and resent.  Kinda hoped it would have made 5.6.

Dan

Re: How to synchronize leds in trigger

[Pavel Machek]

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Hi!

> > I'm happy to invest my time to implement such functionality.
> > I think it can be really useful for LEDs array like CR0014114 <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.5&id=b9dd69155371ebd7055c182e30423edc9104239f>.
> > 
> > In few days I can publish my vision,
> > but before that could you please explain why it will took months?
> > Where it can be hard to implement?
> 
> Just look at how long the API for RGB LEDs is being agreed upon. It is
> over a year already, if not longer, and still not merged.

Sorry about that.

Anyway, you have a pretty good driver with RGB support disabled, IIRC,
and it only had one tiny thing left to fix.

If you want to re-submit that, maybe we can have that for 5.7.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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Re: How to synchronize leds in trigger

[Marek Behun]

On Wed, 26 Feb 2020 15:15:57 +0100
Pavel Machek <pavel@ucw.cz> wrote:

> > Just look at how long the API for RGB LEDs is being agreed upon. It is
> > over a year already, if not longer, and still not merged.  
> 
> Sorry about that.

Hi Pavel,
this was not a complaint, I understand that the problem is compilated,.
Just stating it for Oleh who thought that synchoronizing LED triggers
would be fast work.

> Anyway, you have a pretty good driver with RGB support disabled, IIRC,
> and it only had one tiny thing left to fix.
>
> If you want to re-submit that, maybe we can have that for 5.7.

Yeah, sorry, I had ton of other work to do and then I forgot. I will try
to send patches this week.

Marek