kc.c

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/*
 * PPS kernel consumer API
 *
 * Copyright (C) 2009-2010   Alexander Gordeev <[email protected]>
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#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 */
DEFINE_SPINLOCK(pps_kc_hardpps_lock);
/* PPS API (RFC 2783): current source and mode for kernel consumer */
struct pps_device *pps_kc_hardpps_dev;  /* unique pointer to device */
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);
}