/*
 * 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.
 */


#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/spinlock.h>
#include <linux/idr.h>
#include <linux/fs.h>
#include <linux/pps_kernel.h>
#include <linux/slab.h>

/*
 * Global variables
 */

DEFINE_SPINLOCK(pps_idr_lock);
DEFINE_IDR(pps_idr);

/*
 * 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;
}

/*
 * Exported functions
 */

/* pps_get_source - find a PPS source
 * @source: the PPS source ID.
 *
 * This function is used to find an already registered PPS source into the
 * system.
 *
 * The function returns NULL if found nothing, otherwise it returns a pointer
 * to the PPS source data struct (the refcounter is incremented by 1).
 */

struct pps_device *pps_get_source(int source)
{
        struct pps_device *pps;
        unsigned long flags;

        spin_lock_irqsave(&pps_idr_lock, flags);

        pps = idr_find(&pps_idr, source);
        if (pps != NULL)
                atomic_inc(&pps->usage);

        spin_unlock_irqrestore(&pps_idr_lock, flags);

        return pps;
}

/* pps_put_source - free the PPS source data
 * @pps: a pointer to the PPS source.
 *
 * This function is used to free a PPS data struct if its refcount is 0.
 */

void pps_put_source(struct pps_device *pps)
{
        unsigned long flags;

        spin_lock_irqsave(&pps_idr_lock, flags);
        BUG_ON(atomic_read(&pps->usage) == 0);

        if (!atomic_dec_and_test(&pps->usage)) {
                pps = NULL;
                goto exit;
        }

        /* No more reference to the PPS source. We can safely remove the
         * PPS data struct.
         */
        idr_remove(&pps_idr, pps->id);

exit:
        spin_unlock_irqrestore(&pps_idr_lock, flags);
        kfree(pps);
}

/* 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 source ID.
 */

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

        /* Sanity checks */
        if ((info->mode & default_params) != default_params) {
                printk(KERN_ERR "pps: %s: unsupported default parameters\n",
                                        info->name);
                err = -EINVAL;
                goto pps_register_source_exit;
        }
        if ((info->mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) != 0 &&
                        info->echo == NULL) {
                printk(KERN_ERR "pps: %s: echo function is not defined\n",
                                        info->name);
                err = -EINVAL;
                goto pps_register_source_exit;
        }
        if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
                printk(KERN_ERR "pps: %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_get_new()
         * in order to avoid reces into pps_event().
         */
        pps->params.api_version = PPS_API_VERS;
        pps->params.mode = default_params;
        pps->info = *info;

        init_waitqueue_head(&pps->queue);
        spin_lock_init(&pps->lock);
        atomic_set(&pps->usage, 1);

        /* Get new ID for the new PPS source */
        if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
                err = -ENOMEM;
                goto kfree_pps;
        }

        spin_lock_irq(&pps_idr_lock);

        /* Now really allocate the PPS source.
         * After idr_get_new() calling the new source will be freely available
         * into the kernel.
         */
        err = idr_get_new(&pps_idr, pps, &id);
        if (err < 0) {
                spin_unlock_irq(&pps_idr_lock);
                goto kfree_pps;
        }

        id = id & MAX_ID_MASK;
        if (id >= PPS_MAX_SOURCES) {
                spin_unlock_irq(&pps_idr_lock);

                printk(KERN_ERR "pps: %s: too many PPS sources in the system\n",
                                        info->name);
                err = -EBUSY;
                goto free_idr;
        }
        pps->id = id;

        spin_unlock_irq(&pps_idr_lock);

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

        pr_info("new PPS source %s at ID %d\n", info->name, id);

        return id;

free_idr:
        spin_lock_irq(&pps_idr_lock);
        idr_remove(&pps_idr, id);
        spin_unlock_irq(&pps_idr_lock);

kfree_pps:
        kfree(pps);

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

        return err;
}
EXPORT_SYMBOL(pps_register_source);

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

void pps_unregister_source(int source)
{
        struct pps_device *pps;

        spin_lock_irq(&pps_idr_lock);
        pps = idr_find(&pps_idr, source);

        if (!pps) {
                BUG();
                spin_unlock_irq(&pps_idr_lock);
                return;
        }
        spin_unlock_irq(&pps_idr_lock);

        pps_unregister_cdev(pps);
        pps_put_source(pps);
}
EXPORT_SYMBOL(pps_unregister_source);

/* pps_event - register a PPS event into the system
 * @source: the PPS source ID
 * @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 source it will be called
 * as:
 *      pps->info.echo(source, event, data);
 */

void pps_event(int source, struct pps_ktime *ts, int event, void *data)
{
        struct pps_device *pps;
        unsigned long flags;
        int captured = 0;

        if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
                printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
                        event, source);
                return;
        }

        pps = pps_get_source(source);
        if (!pps)
                return;

        pr_debug("PPS event on source %d at %llu.%06u\n",
                        pps->id, (unsigned long long) ts->sec, ts->nsec);

        spin_lock_irqsave(&pps->lock, flags);

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

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

                /* Save the time stamp */
                pps->assert_tu = *ts;
                pps->assert_sequence++;
                pr_debug("capture assert seq #%u for source %d\n",
                        pps->assert_sequence, source);

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

                /* Save the time stamp */
                pps->clear_tu = *ts;
                pps->clear_sequence++;
                pr_debug("capture clear seq #%u for source %d\n",
                        pps->clear_sequence, source);

                captured = ~0;
        }

        /* Wake up iif captured somthing */
        if (captured) {
                pps->go = ~0;
                wake_up_interruptible(&pps->queue);

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

        spin_unlock_irqrestore(&pps->lock, flags);

        /* Now we can release the PPS source for (possible) deregistration */
        pps_put_source(pps);
}
EXPORT_SYMBOL(pps_event);