posix-clock.c

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/*
 * 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,
};