in clients/pps-gpio.c [223:233]
static int pps_gpio_remove(struct platform_device *pdev)
{
struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
pps_unregister_source(data->pps);
del_timer_sync(&data->echo_timer);
/* reset echo pin in any case */
gpiod_set_value(data->echo_pin, 0);
dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
return 0;
}