/*
   * 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>
  
  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 unsigned int posix_clock_poll(struct file *fp, poll_table *wait)
  {
  	struct posix_clock *clk = get_posix_clock(fp);
  	int result = 0;
  
  	if (!clk)
  		return -ENODEV;
  
  	if (clk->ops.poll)
  		result = clk->ops.poll(clk, fp, wait);
  
  	put_posix_clock(clk);
  
  	return result;
  }
  
  static int posix_clock_fasync(int fd, struct file *fp, int on)
  {
  	struct posix_clock *clk = get_posix_clock(fp);
  	int err = 0;
  
  	if (!clk)
  		return -ENODEV;
  
  	if (clk->ops.fasync)
  		err = clk->ops.fasync(clk, fd, fp, on);
  
  	put_posix_clock(clk);
  
  	return err;
  }
  
  static int posix_clock_mmap(struct file *fp, struct vm_area_struct *vma)
  {
  	struct posix_clock *clk = get_posix_clock(fp);
  	int err = -ENODEV;
  
  	if (!clk)
  		return -ENODEV;
  
  	if (clk->ops.mmap)
  		err = clk->ops.mmap(clk, vma);
  
  	put_posix_clock(clk);
  
  	return err;
  }
  
  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,
  	.fasync		= posix_clock_fasync,
  	.mmap		= posix_clock_mmap,
  #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 timespec *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 timespec *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 timespec *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;
  }
  
  static int pc_timer_create(struct k_itimer *kit)
  {
  	clockid_t id = kit->it_clock;
  	struct posix_clock_desc cd;
  	int err;
  
  	err = get_clock_desc(id, &cd);
  	if (err)
  		return err;
  
  	if (cd.clk->ops.timer_create)
  		err = cd.clk->ops.timer_create(cd.clk, kit);
  	else
  		err = -EOPNOTSUPP;
  
  	put_clock_desc(&cd);
  
  	return err;
  }
  
  static int pc_timer_delete(struct k_itimer *kit)
  {
  	clockid_t id = kit->it_clock;
  	struct posix_clock_desc cd;
  	int err;
  
  	err = get_clock_desc(id, &cd);
  	if (err)
  		return err;
  
  	if (cd.clk->ops.timer_delete)
  		err = cd.clk->ops.timer_delete(cd.clk, kit);
  	else
  		err = -EOPNOTSUPP;
  
  	put_clock_desc(&cd);
  
  	return err;
  }
  
  static void pc_timer_gettime(struct k_itimer *kit, struct itimerspec *ts)
  {
  	clockid_t id = kit->it_clock;
  	struct posix_clock_desc cd;
  
  	if (get_clock_desc(id, &cd))
  		return;
  
  	if (cd.clk->ops.timer_gettime)
  		cd.clk->ops.timer_gettime(cd.clk, kit, ts);
  
  	put_clock_desc(&cd);
  }
  
  static int pc_timer_settime(struct k_itimer *kit, int flags,
  			    struct itimerspec *ts, struct itimerspec *old)
  {
  	clockid_t id = kit->it_clock;
  	struct posix_clock_desc cd;
  	int err;
  
  	err = get_clock_desc(id, &cd);
  	if (err)
  		return err;
  
  	if (cd.clk->ops.timer_settime)
  		err = cd.clk->ops.timer_settime(cd.clk, kit, flags, ts, old);
  	else
  		err = -EOPNOTSUPP;
  
  	put_clock_desc(&cd);
  
  	return err;
  }
  
  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,
  	.timer_create	= pc_timer_create,
  	.timer_set	= pc_timer_settime,
  	.timer_del	= pc_timer_delete,
  	.timer_get	= pc_timer_gettime,
  };