[LinuxPPS] PPS echo implementation

[tom burkart]

Quoting Rodolfo Giometti <giometti at enneenne.com>:

> If you want a patch against Raspberry Pi kernel you should send that  
> patch to Raspberry Pi kernel's maintainers and not to me. I'm a  
> vanilla kernel maintainer and I apply patches to vanilla kernel only.

I felt that the patch may be of wider interest, hence I came here, but  
I also intended to help in testing.

> However, you can add extra Raspberry Pi kernel information to our  
> new LinuxPPS's wiki! :-)

Sounds like a fair deal ;-)
Do I send it to you directly?  What format does it need to be in?

>>>> +        if (of_get_property(np, "enable-pps-echo", NULL)) {
>>>
>>> I think we can safely drop property "enable-pps-echo" and  
>>> considering the EHO functionality activated if property  
>>> "echo-gpios" is present.
>>
>> I elected to provide this functionality as I felt it conceivable  
>> that someone might want the PPS signal but does not want or require  
>> the ECHO functionality.
>
> If I well understand this patch when "enable-pps-echo" is enabled  
> you do a devm_request_threaded_irq(), which in turn calls  
> pps_gpio_irq_threaded() which requires a GPIO line to work...

Oh, yes, of course.  Sorry, I misunderstood the first time around.

Then, if I patch the pps-gpio.dts file directly (as requested), then  
there will always be  an "echo-gpios" present, which then implies that  
the ECHO functionality is always enabled.  Will this be an issue?  Or  
is that why we supply the dts file?

Kind regards,

Tom Burkart
Consultant

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