pps: use BUG_ON for kernel API safety checks

[linux-2.6-block.git] / drivers / pps / kapi.c

/*
 * 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/spinlock.h>
#include <linux/fs.h>
#include <linux/pps_kernel.h>
#include <linux/slab.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;
}

/*
 * 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_ECHOASSERT | PPS_ECHOCLEAR)) != 0 &&
			info->echo == NULL) {
		pr_err("%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) {
		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_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);

	/* 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_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;

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

	dev_dbg(pps->dev, "PPS event at %ld.%09ld\n",
			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_CAPTUREASSERT) &
			(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_CAPTURECLEAR) &
			(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;
	}

	/* 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);