/*
 * posix-clock.c - support for dynamic clock devices
 *
 * Copyright (C) 2010 OMICRON electronics GmbH
 *
 *  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/device.h>
#include <linux/export.h>
#include <linux/file.h>
#include <linux/posix-clock.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>

#include "posix-timers.h"

static void delete_clock(struct kref *kref);

/*
 * Returns NULL if the posix_clock instance attached to 'fp' is old and stale.
 */
static struct posix_clock *get_posix_clock(struct file *fp)
{
        struct posix_clock *clk = fp->private_data;

        down_read(&clk->rwsem);

        if (!clk->zombie)
                return clk;

        up_read(&clk->rwsem);

        return NULL;
}

static void put_posix_clock(struct posix_clock *clk)
{
        up_read(&clk->rwsem);
}

static ssize_t posix_clock_read(struct file *fp, char __user *buf,
                                size_t count, loff_t *ppos)
{
        struct posix_clock *clk = get_posix_clock(fp);
        int err = -EINVAL;

        if (!clk)
                return -ENODEV;

        if (clk->ops.read)
                err = clk->ops.read(clk, fp->f_flags, buf, count);

        put_posix_clock(clk);

        return err;
}

static __poll_t posix_clock_poll(struct file *fp, poll_table *wait)
{
        struct posix_clock *clk = get_posix_clock(fp);
        __poll_t result = 0;

        if (!clk)
                return EPOLLERR;

        if (clk->ops.poll)
                result = clk->ops.poll(clk, fp, wait);

        put_posix_clock(clk);

        return result;
}

static long posix_clock_ioctl(struct file *fp,
                              unsigned int cmd, unsigned long arg)
{
        struct posix_clock *clk = get_posix_clock(fp);
        int err = -ENOTTY;

        if (!clk)
                return -ENODEV;

        if (clk->ops.ioctl)
                err = clk->ops.ioctl(clk, cmd, arg);

        put_posix_clock(clk);

        return err;
}

#ifdef CONFIG_COMPAT
static long posix_clock_compat_ioctl(struct file *fp,
                                     unsigned int cmd, unsigned long arg)
{
        struct posix_clock *clk = get_posix_clock(fp);
        int err = -ENOTTY;

        if (!clk)
                return -ENODEV;

        if (clk->ops.ioctl)
                err = clk->ops.ioctl(clk, cmd, arg);

        put_posix_clock(clk);

        return err;
}
#endif

static int posix_clock_open(struct inode *inode, struct file *fp)
{
        int err;
        struct posix_clock *clk =
                container_of(inode->i_cdev, struct posix_clock, cdev);

        down_read(&clk->rwsem);

        if (clk->zombie) {
                err = -ENODEV;
                goto out;
        }
        if (clk->ops.open)
                err = clk->ops.open(clk, fp->f_mode);
        else
                err = 0;

        if (!err) {
                kref_get(&clk->kref);
                fp->private_data = clk;
        }
out:
        up_read(&clk->rwsem);
        return err;
}

static int posix_clock_release(struct inode *inode, struct file *fp)
{
        struct posix_clock *clk = fp->private_data;
        int err = 0;

        if (clk->ops.release)
                err = clk->ops.release(clk);

        kref_put(&clk->kref, delete_clock);

        fp->private_data = NULL;

        return err;
}

static const struct file_operations posix_clock_file_operations = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .read           = posix_clock_read,
        .poll           = posix_clock_poll,
        .unlocked_ioctl = posix_clock_ioctl,
        .open           = posix_clock_open,
        .release        = posix_clock_release,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = posix_clock_compat_ioctl,
#endif
};

int posix_clock_register(struct posix_clock *clk, dev_t devid)
{
        int err;

        kref_init(&clk->kref);
        init_rwsem(&clk->rwsem);

        cdev_init(&clk->cdev, &posix_clock_file_operations);
        clk->cdev.owner = clk->ops.owner;
        err = cdev_add(&clk->cdev, devid, 1);

        return err;
}
EXPORT_SYMBOL_GPL(posix_clock_register);

static void delete_clock(struct kref *kref)
{
        struct posix_clock *clk = container_of(kref, struct posix_clock, kref);

        if (clk->release)
                clk->release(clk);
}

void posix_clock_unregister(struct posix_clock *clk)
{
        cdev_del(&clk->cdev);

        down_write(&clk->rwsem);
        clk->zombie = true;
        up_write(&clk->rwsem);

        kref_put(&clk->kref, delete_clock);
}
EXPORT_SYMBOL_GPL(posix_clock_unregister);

struct posix_clock_desc {
        struct file *fp;
        struct posix_clock *clk;
};

static int get_clock_desc(const clockid_t id, struct posix_clock_desc *cd)
{
        struct file *fp = fget(clockid_to_fd(id));
        int err = -EINVAL;

        if (!fp)
                return err;

        if (fp->f_op->open != posix_clock_open || !fp->private_data)
                goto out;

        cd->fp = fp;
        cd->clk = get_posix_clock(fp);

        err = cd->clk ? 0 : -ENODEV;
out:
        if (err)
                fput(fp);
        return err;
}

static void put_clock_desc(struct posix_clock_desc *cd)
{
        put_posix_clock(cd->clk);
        fput(cd->fp);
}

static int pc_clock_adjtime(clockid_t id, struct timex *tx)
{
        struct posix_clock_desc cd;
        int err;

        err = get_clock_desc(id, &cd);
        if (err)
                return err;

        if ((cd.fp->f_mode & FMODE_WRITE) == 0) {
                err = -EACCES;
                goto out;
        }

        if (cd.clk->ops.clock_adjtime)
                err = cd.clk->ops.clock_adjtime(cd.clk, tx);
        else
                err = -EOPNOTSUPP;
out:
        put_clock_desc(&cd);

        return err;
}

static int pc_clock_gettime(clockid_t id, struct timespec64 *ts)
{
        struct posix_clock_desc cd;
        int err;

        err = get_clock_desc(id, &cd);
        if (err)
                return err;

        if (cd.clk->ops.clock_gettime)
                err = cd.clk->ops.clock_gettime(cd.clk, ts);
        else
                err = -EOPNOTSUPP;

        put_clock_desc(&cd);

        return err;
}

static int pc_clock_getres(clockid_t id, struct timespec64 *ts)
{
        struct posix_clock_desc cd;
        int err;

        err = get_clock_desc(id, &cd);
        if (err)
                return err;

        if (cd.clk->ops.clock_getres)
                err = cd.clk->ops.clock_getres(cd.clk, ts);
        else
                err = -EOPNOTSUPP;

        put_clock_desc(&cd);

        return err;
}

static int pc_clock_settime(clockid_t id, const struct timespec64 *ts)
{
        struct posix_clock_desc cd;
        int err;

        err = get_clock_desc(id, &cd);
        if (err)
                return err;

        if ((cd.fp->f_mode & FMODE_WRITE) == 0) {
                err = -EACCES;
                goto out;
        }

        if (cd.clk->ops.clock_settime)
                err = cd.clk->ops.clock_settime(cd.clk, ts);
        else
                err = -EOPNOTSUPP;
out:
        put_clock_desc(&cd);

        return err;
}

const struct k_clock clock_posix_dynamic = {
        .clock_getres   = pc_clock_getres,
        .clock_set      = pc_clock_settime,
        .clock_get      = pc_clock_gettime,
        .clock_adj      = pc_clock_adjtime,
};