/*
 * kernel API
 *
 *
 * Copyright (C) 2005-2009   Rodolfo Giometti <giometti@linux.it>
 *
 *   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/init.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/spinlock.h>
#include <linux/fs.h>
#include <linux/pps_kernel.h>
#include <linux/slab.h>

#include "kc.h"

/*
 * Local functions
 */

static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
{
        ts->nsec += offset->nsec;
        while (ts->nsec >= NSEC_PER_SEC) {
                ts->nsec -= NSEC_PER_SEC;
                ts->sec++;
        }
        while (ts->nsec < 0) {
                ts->nsec += NSEC_PER_SEC;
                ts->sec--;
        }
        ts->sec += offset->sec;
}

static void pps_echo_client_default(struct pps_device *pps, int event,
                void *data)
{
        dev_info(pps->dev, "echo %s %s\n",
                event & PPS_CAPTUREASSERT ? "assert" : "",
                event & PPS_CAPTURECLEAR ? "clear" : "");
}

/*
 * Exported functions
 */

/* pps_register_source - add a PPS source in the system
 * @info: the PPS info struct
 * @default_params: the default PPS parameters of the new source
 *
 * This function is used to add a new PPS source in the system. The new
 * source is described by info's fields and it will have, as default PPS
 * parameters, the ones specified into default_params.
 *
 * The function returns, in case of success, the PPS device. Otherwise NULL.
 */

struct pps_device *pps_register_source(struct pps_source_info *info,
                int default_params)
{
        struct pps_device *pps;
        int err;

        /* Sanity checks */
        if ((info->mode & default_params) != default_params) {
                pr_err("%s: unsupported default parameters\n",
                                        info->name);
                err = -EINVAL;
                goto pps_register_source_exit;
        }
        if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
                pr_err("%s: unspecified time format\n",
                                        info->name);
                err = -EINVAL;
                goto pps_register_source_exit;
        }

        /* Allocate memory for the new PPS source struct */
        pps = kzalloc(sizeof(struct pps_device), GFP_KERNEL);
        if (pps == NULL) {
                err = -ENOMEM;
                goto pps_register_source_exit;
        }

        /* These initializations must be done before calling idr_alloc()
         * in order to avoid reces into pps_event().
         */
        pps->params.api_version = PPS_API_VERS;
        pps->params.mode = default_params;
        pps->info = *info;

        /* check for default echo function */
        if ((pps->info.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) &&
                        pps->info.echo == NULL)
                pps->info.echo = pps_echo_client_default;

        init_waitqueue_head(&pps->queue);
        spin_lock_init(&pps->lock);

        /* Create the char device */
        err = pps_register_cdev(pps);
        if (err < 0) {
                pr_err("%s: unable to create char device\n",
                                        info->name);
                goto kfree_pps;
        }

        dev_info(pps->dev, "new PPS source %s\n", info->name);

        return pps;

kfree_pps:
        kfree(pps);

pps_register_source_exit:
        pr_err("%s: unable to register source\n", info->name);

        return NULL;
}
EXPORT_SYMBOL(pps_register_source);

/* pps_unregister_source - remove a PPS source from the system
 * @pps: the PPS source
 *
 * This function is used to remove a previously registered PPS source from
 * the system.
 */

void pps_unregister_source(struct pps_device *pps)
{
        pps_kc_remove(pps);
        pps_unregister_cdev(pps);

        /* don't have to kfree(pps) here because it will be done on
         * device destruction */
}
EXPORT_SYMBOL(pps_unregister_source);

/* pps_event - register a PPS event into the system
 * @pps: the PPS device
 * @ts: the event timestamp
 * @event: the event type
 * @data: userdef pointer
 *
 * This function is used by each PPS client in order to register a new
 * PPS event into the system (it's usually called inside an IRQ handler).
 *
 * If an echo function is associated with the PPS device it will be called
 * as:
 *      pps->info.echo(pps, event, data);
 */
void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
                void *data)
{
        unsigned long flags;
        int captured = 0;
        struct pps_ktime ts_real = { .sec = 0, .nsec = 0, .flags = 0 };

        /* check event type */
        BUG_ON((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0);

        dev_dbg(pps->dev, "PPS event at %lld.%09ld\n",
                        (s64)ts->ts_real.tv_sec, ts->ts_real.tv_nsec);

        timespec_to_pps_ktime(&ts_real, ts->ts_real);

        spin_lock_irqsave(&pps->lock, flags);

        /* Must call the echo function? */
        if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
                pps->info.echo(pps, event, data);

        /* Check the event */
        pps->current_mode = pps->params.mode;
        if (event & pps->params.mode & PPS_CAPTUREASSERT) {
                /* We have to add an offset? */
                if (pps->params.mode & PPS_OFFSETASSERT)
                        pps_add_offset(&ts_real,
                                        &pps->params.assert_off_tu);

                /* Save the time stamp */
                pps->assert_tu = ts_real;
                pps->assert_sequence++;
                dev_dbg(pps->dev, "capture assert seq #%u\n",
                        pps->assert_sequence);

                captured = ~0;
        }
        if (event & pps->params.mode & PPS_CAPTURECLEAR) {
                /* We have to add an offset? */
                if (pps->params.mode & PPS_OFFSETCLEAR)
                        pps_add_offset(&ts_real,
                                        &pps->params.clear_off_tu);

                /* Save the time stamp */
                pps->clear_tu = ts_real;
                pps->clear_sequence++;
                dev_dbg(pps->dev, "capture clear seq #%u\n",
                        pps->clear_sequence);

                captured = ~0;
        }

        pps_kc_event(pps, ts, event);

        /* Wake up if captured something */
        if (captured) {
                pps->last_ev++;
                wake_up_interruptible_all(&pps->queue);

                kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
        }

        spin_unlock_irqrestore(&pps->lock, flags);
}
EXPORT_SYMBOL(pps_event);