xref: /kernel/linux/linux-5.10/drivers/pps/kc.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * PPS kernel consumer API
 *
 * Copyright (C) 2009-2010   Alexander Gordeev <lasaine@lvk.cs.msu.su>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/pps_kernel.h>

#include "kc.h"

/*
 * Global variables
 */

/* state variables to bind kernel consumer */
static DEFINE_SPINLOCK(pps_kc_hardpps_lock);
/* PPS API (RFC 2783): current source and mode for kernel consumer */
static struct pps_device *pps_kc_hardpps_dev;	/* unique pointer to device */
static int pps_kc_hardpps_mode;		/* mode bits for kernel consumer */

/* pps_kc_bind - control PPS kernel consumer binding
 * @pps: the PPS source
 * @bind_args: kernel consumer bind parameters
 *
 * This function is used to bind or unbind PPS kernel consumer according to
 * supplied parameters. Should not be called in interrupt context.
 */
int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args)
{
	/* Check if another consumer is already bound */
	spin_lock_irq(&pps_kc_hardpps_lock);

	if (bind_args->edge == 0)
		if (pps_kc_hardpps_dev == pps) {
			pps_kc_hardpps_mode = 0;
			pps_kc_hardpps_dev = NULL;
			spin_unlock_irq(&pps_kc_hardpps_lock);
			dev_info(pps->dev, "unbound kernel"
					" consumer\n");
		} else {
			spin_unlock_irq(&pps_kc_hardpps_lock);
			dev_err(pps->dev, "selected kernel consumer"
					" is not bound\n");
			return -EINVAL;
		}
	else
		if (pps_kc_hardpps_dev == NULL ||
				pps_kc_hardpps_dev == pps) {
			pps_kc_hardpps_mode = bind_args->edge;
			pps_kc_hardpps_dev = pps;
			spin_unlock_irq(&pps_kc_hardpps_lock);
			dev_info(pps->dev, "bound kernel consumer: "
				"edge=0x%x\n", bind_args->edge);
		} else {
			spin_unlock_irq(&pps_kc_hardpps_lock);
			dev_err(pps->dev, "another kernel consumer"
					" is already bound\n");
			return -EINVAL;
		}

	return 0;
}

/* pps_kc_remove - unbind kernel consumer on PPS source removal
 * @pps: the PPS source
 *
 * This function is used to disable kernel consumer on PPS source removal
 * if this source was bound to PPS kernel consumer. Can be called on any
 * source safely. Should not be called in interrupt context.
 */
void pps_kc_remove(struct pps_device *pps)
{
	spin_lock_irq(&pps_kc_hardpps_lock);
	if (pps == pps_kc_hardpps_dev) {
		pps_kc_hardpps_mode = 0;
		pps_kc_hardpps_dev = NULL;
		spin_unlock_irq(&pps_kc_hardpps_lock);
		dev_info(pps->dev, "unbound kernel consumer"
				" on device removal\n");
	} else
		spin_unlock_irq(&pps_kc_hardpps_lock);
}

/* pps_kc_event - call hardpps() on PPS event
 * @pps: the PPS source
 * @ts: PPS event timestamp
 * @event: PPS event edge
 *
 * This function calls hardpps() when an event from bound PPS source occurs.
 */
void pps_kc_event(struct pps_device *pps, struct pps_event_time *ts,
		int event)
{
	unsigned long flags;

	/* Pass some events to kernel consumer if activated */
	spin_lock_irqsave(&pps_kc_hardpps_lock, flags);
	if (pps == pps_kc_hardpps_dev && event & pps_kc_hardpps_mode)
		hardpps(&ts->ts_real, &ts->ts_raw);
	spin_unlock_irqrestore(&pps_kc_hardpps_lock, flags);
}