[RFE] Enable CONFIG_PPS_CLIENT_GPIO in kernel

[space55]

Current situation

Currently, CONFIG_PPS_CLIENT_GPIO is not set, which causes PPS services to be unavailable.

Impact

I am in progress with trying to make a GPS-disciplined network clock on a Raspberry Pi, using chronyd and gpsd. This requires a PPS device to be created in /dev, which gpsd can then use to synchronize with a serial device. I am unable to load the module pps-gpio which exists on Raspbian.

Ideal future situation

Ideally, I would be able to create a /dev/pps0 device that can be used by gpsd to control chrony & set the RTC accurately.

Implementation options

The primary method I can think of is to change the kernel build config setting to set CONFIG_PPS_CLIENT_GPIO=y

Additional information

$ modprobe pps-gpio
libkmod: kmod_config_parse: /etc/modprobe.d/gpio.conf line 1: ignoring bad line starting with 'pps_gpio'
modprobe: FATAL: Module pps-gpio not found in directory /lib/modules/6.1.85-flatcar

System info:

$ cat /etc/os-release
NAME="Flatcar Container Linux by Kinvolk"
ID=flatcar
ID_LIKE=coreos
VERSION=3815.2.2
VERSION_ID=3815.2.2
BUILD_ID=2024-04-13-1325
SYSEXT_LEVEL=1.0
PRETTY_NAME="Flatcar Container Linux by Kinvolk 3815.2.2 (Oklo)"
ANSI_COLOR="38;5;75"
HOME_URL="https://flatcar.org/"
BUG_REPORT_URL="https://issues.flatcar.org"
FLATCAR_BOARD="arm64-usr"
CPE_NAME="cpe:2.3:o:flatcar-linux:flatcar_linux:3815.2.2:*:*:*:*:*:*:*"

If there are any questions, or anything I can do/test, please let me know!

[pothos]

The file to enable this would be sdk_container/src/third_party/coreos-overlay/sys-kernel/coreos-modules/files/commonconfig-6.6 or sdk_container/src/third_party/coreos-overlay/sys-kernel/coreos-modules/files/arm64_defconfig-6.6 in the scripts repo.
Before being able to merge such a change we need to keep an eye on the filesystem usage of the boot partition (The CI for the scripts repo produces an image report artifact which reports size changes).

[ader1990]

Hello, on my Orange PI, this is the size of the module - should be fine size-wise, but we need to cross check:

ls -liath /lib/modules/5.10.160-rockchip/kernel/drivers/pps/clients/pps-gpio.ko
284324 -rw-r--r-- 1 root root 13K Mar 21 15:57 /lib/modules/5.10.160-rockchip/kernel/drivers/pps/clients/pps-gpio.ko

[pothos]

Thanks, if it's just a module it won't be in the initrd and things are good.