linux-kernel - pps-gpio falsely reporting echo capability?

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Date:   Tue, 30 Jan 2018 19:14:16 +0100
From:   Lukas Senger <lukas@...dolin.com>
To:     giometti@...eenne.com
Cc:     linux-kernel@...r.kernel.org
Subject: pps-gpio falsely reporting echo capability?

Hi,

I'm trying to use PPS_ECHOASSERT with the GPIO pins on a Raspberry
Pi. /sys/class/pps/pps0/echo reports 1, however looking at pps-gpio.c,
no echo-callback is registered. Am I missing something or should either
sysfs report 0 or pps echo be implemented in the client?

>From a quick glance at the other clients, the same might be true for
pps-ktimer and pps_parport. They both report PPS_ECHO* in info.mode but
never define info.echo.

Cheers,
Lukas