V4L/DVB (4282): Fix: use swzigzag for swalgo

[linux-2.6/btrfs-unstable.git] / drivers / media / dvb / dvb-core / dvb_frontend.c

/*
 * dvb_frontend.c: DVB frontend tuning interface/thread
 *
 *
 * Copyright (C) 1999-2001 Ralph  Metzler
 *                         Marcus Metzler
 *                         Holger Waechtler
 *                                    for convergence integrated media GmbH
 *
 * Copyright (C) 2004 Andrew de Quincey (tuning thread cleanup)
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 * Or, point your browser to http://www.gnu.org/copyleft/gpl.html
 */

#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/list.h>
#include <linux/suspend.h>
#include <linux/jiffies.h>
#include <asm/processor.h>

#include "dvb_frontend.h"
#include "dvbdev.h"

static int dvb_frontend_debug;
static int dvb_shutdown_timeout = 5;
static int dvb_force_auto_inversion;
static int dvb_override_tune_delay;
static int dvb_powerdown_on_sleep = 1;

module_param_named(frontend_debug, dvb_frontend_debug, int, 0644);
MODULE_PARM_DESC(frontend_debug, "Turn on/off frontend core debugging (default:off).");
module_param(dvb_shutdown_timeout, int, 0644);
MODULE_PARM_DESC(dvb_shutdown_timeout, "wait <shutdown_timeout> seconds after close() before suspending hardware");
module_param(dvb_force_auto_inversion, int, 0644);
MODULE_PARM_DESC(dvb_force_auto_inversion, "0: normal (default), 1: INVERSION_AUTO forced always");
module_param(dvb_override_tune_delay, int, 0644);
MODULE_PARM_DESC(dvb_override_tune_delay, "0: normal (default), >0 => delay in milliseconds to wait for lock after a tune attempt");
module_param(dvb_powerdown_on_sleep, int, 0644);
MODULE_PARM_DESC(dvb_powerdown_on_sleep, "0: do not power down, 1: turn LNB voltage off on sleep (default)");

#define dprintk if (dvb_frontend_debug) printk

#define FESTATE_IDLE 1
#define FESTATE_RETUNE 2
#define FESTATE_TUNING_FAST 4
#define FESTATE_TUNING_SLOW 8
#define FESTATE_TUNED 16
#define FESTATE_ZIGZAG_FAST 32
#define FESTATE_ZIGZAG_SLOW 64
#define FESTATE_DISEQC 128
#define FESTATE_WAITFORLOCK (FESTATE_TUNING_FAST | FESTATE_TUNING_SLOW | FESTATE_ZIGZAG_FAST | FESTATE_ZIGZAG_SLOW | FESTATE_DISEQC)
#define FESTATE_SEARCHING_FAST (FESTATE_TUNING_FAST | FESTATE_ZIGZAG_FAST)
#define FESTATE_SEARCHING_SLOW (FESTATE_TUNING_SLOW | FESTATE_ZIGZAG_SLOW)
#define FESTATE_LOSTLOCK (FESTATE_ZIGZAG_FAST | FESTATE_ZIGZAG_SLOW)

#define FE_ALGO_HW              1
/*
 * FESTATE_IDLE. No tuning parameters have been supplied and the loop is idling.
 * FESTATE_RETUNE. Parameters have been supplied, but we have not yet performed the first tune.
 * FESTATE_TUNING_FAST. Tuning parameters have been supplied and fast zigzag scan is in progress.
 * FESTATE_TUNING_SLOW. Tuning parameters have been supplied. Fast zigzag failed, so we're trying again, but slower.
 * FESTATE_TUNED. The frontend has successfully locked on.
 * FESTATE_ZIGZAG_FAST. The lock has been lost, and a fast zigzag has been initiated to try and regain it.
 * FESTATE_ZIGZAG_SLOW. The lock has been lost. Fast zigzag has been failed, so we're trying again, but slower.
 * FESTATE_DISEQC. A DISEQC command has just been issued.
 * FESTATE_WAITFORLOCK. When we're waiting for a lock.
 * FESTATE_SEARCHING_FAST. When we're searching for a signal using a fast zigzag scan.
 * FESTATE_SEARCHING_SLOW. When we're searching for a signal using a slow zigzag scan.
 * FESTATE_LOSTLOCK. When the lock has been lost, and we're searching it again.
 */

static DEFINE_MUTEX(frontend_mutex);

struct dvb_frontend_private {

        /* thread/frontend values */
        struct dvb_device *dvbdev;
        struct dvb_frontend_parameters parameters;
        struct dvb_fe_events events;
        struct semaphore sem;
        struct list_head list_head;
        wait_queue_head_t wait_queue;
        pid_t thread_pid;
        unsigned long release_jiffies;
        unsigned int exit;
        unsigned int wakeup;
        fe_status_t status;
        unsigned long tune_mode_flags;
        unsigned int delay;
        unsigned int reinitialise;
        int tone;
        int voltage;

        /* swzigzag values */
        unsigned int state;
        unsigned int bending;
        int lnb_drift;
        unsigned int inversion;
        unsigned int auto_step;
        unsigned int auto_sub_step;
        unsigned int started_auto_step;
        unsigned int min_delay;
        unsigned int max_drift;
        unsigned int step_size;
        int quality;
        unsigned int check_wrapped;
};

static void dvb_frontend_wakeup(struct dvb_frontend *fe);

static void dvb_frontend_add_event(struct dvb_frontend *fe, fe_status_t status)
{
        struct dvb_frontend_private *fepriv = fe->frontend_priv;
        struct dvb_fe_events *events = &fepriv->events;
        struct dvb_frontend_event *e;
        int wp;

        dprintk ("%s\n", __FUNCTION__);

        if (down_interruptible (&events->sem))
                return;

        wp = (events->eventw + 1) % MAX_EVENT;

        if (wp == events->eventr) {
                events->overflow = 1;
                events->eventr = (events->eventr + 1) % MAX_EVENT;
        }

        e = &events->events[events->eventw];

        memcpy (&e->parameters, &fepriv->parameters,
                sizeof (struct dvb_frontend_parameters));

        if (status & FE_HAS_LOCK)
                if (fe->ops.get_frontend)
                        fe->ops.get_frontend(fe, &e->parameters);

        events->eventw = wp;

        up (&events->sem);

        e->status = status;

        wake_up_interruptible (&events->wait_queue);
}

static int dvb_frontend_get_event(struct dvb_frontend *fe,
                            struct dvb_frontend_event *event, int flags)
{
        struct dvb_frontend_private *fepriv = fe->frontend_priv;
        struct dvb_fe_events *events = &fepriv->events;

        dprintk ("%s\n", __FUNCTION__);

        if (events->overflow) {
                events->overflow = 0;
                return -EOVERFLOW;
        }

        if (events->eventw == events->eventr) {
                int ret;

                if (flags & O_NONBLOCK)
                        return -EWOULDBLOCK;

                up(&fepriv->sem);

                ret = wait_event_interruptible (events->wait_queue,
                                                events->eventw != events->eventr);

                if (down_interruptible (&fepriv->sem))
                        return -ERESTARTSYS;

                if (ret < 0)
                        return ret;
        }

        if (down_interruptible (&events->sem))
                return -ERESTARTSYS;

        memcpy (event, &events->events[events->eventr],
                sizeof(struct dvb_frontend_event));

        events->eventr = (events->eventr + 1) % MAX_EVENT;

        up (&events->sem);

        return 0;
}

static void dvb_frontend_init(struct dvb_frontend *fe)
{
        dprintk ("DVB: initialising frontend %i (%s)...\n",
                 fe->dvb->num,
                 fe->ops.info.name);

        if (fe->ops.init)
                fe->ops.init(fe);
        if (fe->ops.tuner_ops.init) {
                fe->ops.tuner_ops.init(fe);
                if (fe->ops.i2c_gate_ctrl)
                        fe->ops.i2c_gate_ctrl(fe, 0);
        }
}

void dvb_frontend_reinitialise(struct dvb_frontend *fe)
{
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        fepriv->reinitialise = 1;
        dvb_frontend_wakeup(fe);
}
EXPORT_SYMBOL(dvb_frontend_reinitialise);

static void dvb_frontend_swzigzag_update_delay(struct dvb_frontend_private *fepriv, int locked)
{
        int q2;

        dprintk ("%s\n", __FUNCTION__);

        if (locked)
                (fepriv->quality) = (fepriv->quality * 220 + 36*256) / 256;
        else
                (fepriv->quality) = (fepriv->quality * 220 + 0) / 256;

        q2 = fepriv->quality - 128;
        q2 *= q2;

        fepriv->delay = fepriv->min_delay + q2 * HZ / (128*128);
}

/**
 * Performs automatic twiddling of frontend parameters.
 *
 * @param fe The frontend concerned.
 * @param check_wrapped Checks if an iteration has completed. DO NOT SET ON THE FIRST ATTEMPT
 * @returns Number of complete iterations that have been performed.
 */
static int dvb_frontend_swzigzag_autotune(struct dvb_frontend *fe, int check_wrapped)
{
        int autoinversion;
        int ready = 0;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;
        int original_inversion = fepriv->parameters.inversion;
        u32 original_frequency = fepriv->parameters.frequency;

        /* are we using autoinversion? */
        autoinversion = ((!(fe->ops.info.caps & FE_CAN_INVERSION_AUTO)) &&
                         (fepriv->parameters.inversion == INVERSION_AUTO));

        /* setup parameters correctly */
        while(!ready) {
                /* calculate the lnb_drift */
                fepriv->lnb_drift = fepriv->auto_step * fepriv->step_size;

                /* wrap the auto_step if we've exceeded the maximum drift */
                if (fepriv->lnb_drift > fepriv->max_drift) {
                        fepriv->auto_step = 0;
                        fepriv->auto_sub_step = 0;
                        fepriv->lnb_drift = 0;
                }

                /* perform inversion and +/- zigzag */
                switch(fepriv->auto_sub_step) {
                case 0:
                        /* try with the current inversion and current drift setting */
                        ready = 1;
                        break;

                case 1:
                        if (!autoinversion) break;

                        fepriv->inversion = (fepriv->inversion == INVERSION_OFF) ? INVERSION_ON : INVERSION_OFF;
                        ready = 1;
                        break;

                case 2:
                        if (fepriv->lnb_drift == 0) break;

                        fepriv->lnb_drift = -fepriv->lnb_drift;
                        ready = 1;
                        break;

                case 3:
                        if (fepriv->lnb_drift == 0) break;
                        if (!autoinversion) break;

                        fepriv->inversion = (fepriv->inversion == INVERSION_OFF) ? INVERSION_ON : INVERSION_OFF;
                        fepriv->lnb_drift = -fepriv->lnb_drift;
                        ready = 1;
                        break;

                default:
                        fepriv->auto_step++;
                        fepriv->auto_sub_step = -1; /* it'll be incremented to 0 in a moment */
                        break;
                }

                if (!ready) fepriv->auto_sub_step++;
        }

        /* if this attempt would hit where we started, indicate a complete
         * iteration has occurred */
        if ((fepriv->auto_step == fepriv->started_auto_step) &&
            (fepriv->auto_sub_step == 0) && check_wrapped) {
                return 1;
        }

        dprintk("%s: drift:%i inversion:%i auto_step:%i "
                "auto_sub_step:%i started_auto_step:%i\n",
                __FUNCTION__, fepriv->lnb_drift, fepriv->inversion,
                fepriv->auto_step, fepriv->auto_sub_step, fepriv->started_auto_step);

        /* set the frontend itself */
        fepriv->parameters.frequency += fepriv->lnb_drift;
        if (autoinversion)
                fepriv->parameters.inversion = fepriv->inversion;
        if (fe->ops.set_frontend)
                fe->ops.set_frontend(fe, &fepriv->parameters);

        fepriv->parameters.frequency = original_frequency;
        fepriv->parameters.inversion = original_inversion;

        fepriv->auto_sub_step++;
        return 0;
}

static void dvb_frontend_swzigzag(struct dvb_frontend *fe)
{
        fe_status_t s;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        /* if we've got no parameters, just keep idling */
        if (fepriv->state & FESTATE_IDLE) {
                fepriv->delay = 3*HZ;
                fepriv->quality = 0;
                return;
        }

        /* in SCAN mode, we just set the frontend when asked and leave it alone */
        if (fepriv->tune_mode_flags & FE_TUNE_MODE_ONESHOT) {
                if (fepriv->state & FESTATE_RETUNE) {
                        if (fe->ops.set_frontend)
                                fe->ops.set_frontend(fe, &fepriv->parameters);
                        fepriv->state = FESTATE_TUNED;
                }
                fepriv->delay = 3*HZ;
                fepriv->quality = 0;
                return;
        }

        /* get the frontend status */
        if (fepriv->state & FESTATE_RETUNE) {
                s = 0;
        } else {
                if (fe->ops.read_status)
                        fe->ops.read_status(fe, &s);
                if (s != fepriv->status) {
                        dvb_frontend_add_event(fe, s);
                        fepriv->status = s;
                }
        }

        /* if we're not tuned, and we have a lock, move to the TUNED state */
        if ((fepriv->state & FESTATE_WAITFORLOCK) && (s & FE_HAS_LOCK)) {
                dvb_frontend_swzigzag_update_delay(fepriv, s & FE_HAS_LOCK);
                fepriv->state = FESTATE_TUNED;

                /* if we're tuned, then we have determined the correct inversion */
                if ((!(fe->ops.info.caps & FE_CAN_INVERSION_AUTO)) &&
                    (fepriv->parameters.inversion == INVERSION_AUTO)) {
                        fepriv->parameters.inversion = fepriv->inversion;
                }
                return;
        }

        /* if we are tuned already, check we're still locked */
        if (fepriv->state & FESTATE_TUNED) {
                dvb_frontend_swzigzag_update_delay(fepriv, s & FE_HAS_LOCK);

                /* we're tuned, and the lock is still good... */
                if (s & FE_HAS_LOCK) {
                        return;
                } else { /* if we _WERE_ tuned, but now don't have a lock */
                        fepriv->state = FESTATE_ZIGZAG_FAST;
                        fepriv->started_auto_step = fepriv->auto_step;
                        fepriv->check_wrapped = 0;
                }
        }

        /* don't actually do anything if we're in the LOSTLOCK state,
         * the frontend is set to FE_CAN_RECOVER, and the max_drift is 0 */
        if ((fepriv->state & FESTATE_LOSTLOCK) &&
            (fe->ops.info.caps & FE_CAN_RECOVER) && (fepriv->max_drift == 0)) {
                dvb_frontend_swzigzag_update_delay(fepriv, s & FE_HAS_LOCK);
                return;
        }

        /* don't do anything if we're in the DISEQC state, since this
         * might be someone with a motorized dish controlled by DISEQC.
         * If its actually a re-tune, there will be a SET_FRONTEND soon enough. */
        if (fepriv->state & FESTATE_DISEQC) {
                dvb_frontend_swzigzag_update_delay(fepriv, s & FE_HAS_LOCK);
                return;
        }

        /* if we're in the RETUNE state, set everything up for a brand
         * new scan, keeping the current inversion setting, as the next
         * tune is _very_ likely to require the same */
        if (fepriv->state & FESTATE_RETUNE) {
                fepriv->lnb_drift = 0;
                fepriv->auto_step = 0;
                fepriv->auto_sub_step = 0;
                fepriv->started_auto_step = 0;
                fepriv->check_wrapped = 0;
        }

        /* fast zigzag. */
        if ((fepriv->state & FESTATE_SEARCHING_FAST) || (fepriv->state & FESTATE_RETUNE)) {
                fepriv->delay = fepriv->min_delay;

                /* peform a tune */
                if (dvb_frontend_swzigzag_autotune(fe, fepriv->check_wrapped)) {
                        /* OK, if we've run out of trials at the fast speed.
                         * Drop back to slow for the _next_ attempt */
                        fepriv->state = FESTATE_SEARCHING_SLOW;
                        fepriv->started_auto_step = fepriv->auto_step;
                        return;
                }
                fepriv->check_wrapped = 1;

                /* if we've just retuned, enter the ZIGZAG_FAST state.
                 * This ensures we cannot return from an
                 * FE_SET_FRONTEND ioctl before the first frontend tune
                 * occurs */
                if (fepriv->state & FESTATE_RETUNE) {
                        fepriv->state = FESTATE_TUNING_FAST;
                }
        }

        /* slow zigzag */
        if (fepriv->state & FESTATE_SEARCHING_SLOW) {
                dvb_frontend_swzigzag_update_delay(fepriv, s & FE_HAS_LOCK);

                /* Note: don't bother checking for wrapping; we stay in this
                 * state until we get a lock */
                dvb_frontend_swzigzag_autotune(fe, 0);
        }
}

static int dvb_frontend_is_exiting(struct dvb_frontend *fe)
{
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        if (fepriv->exit)
                return 1;

        if (fepriv->dvbdev->writers == 1)
                if (time_after(jiffies, fepriv->release_jiffies +
                                  dvb_shutdown_timeout * HZ))
                        return 1;

        return 0;
}

static int dvb_frontend_should_wakeup(struct dvb_frontend *fe)
{
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        if (fepriv->wakeup) {
                fepriv->wakeup = 0;
                return 1;
        }
        return dvb_frontend_is_exiting(fe);
}

static void dvb_frontend_wakeup(struct dvb_frontend *fe)
{
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        fepriv->wakeup = 1;
        wake_up_interruptible(&fepriv->wait_queue);
}

static int dvb_frontend_thread(void *data)
{
        struct dvb_frontend *fe = data;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;
        unsigned long timeout;
        char name [15];
        fe_status_t s;
        struct dvb_frontend_parameters *params;

        dprintk("%s\n", __FUNCTION__);

        snprintf (name, sizeof(name), "kdvb-fe-%i", fe->dvb->num);

        lock_kernel();
        daemonize(name);
        sigfillset(&current->blocked);
        unlock_kernel();

        fepriv->check_wrapped = 0;
        fepriv->quality = 0;
        fepriv->delay = 3*HZ;
        fepriv->status = 0;
        fepriv->wakeup = 0;
        fepriv->reinitialise = 1;

        while (1) {
                up(&fepriv->sem);           /* is locked when we enter the thread... */

                timeout = wait_event_interruptible_timeout(fepriv->wait_queue,
                                                           dvb_frontend_should_wakeup(fe),
                                                           fepriv->delay);
                if (0 != dvb_frontend_is_exiting(fe)) {
                        /* got signal or quitting */
                        break;
                }

                try_to_freeze();

                if (down_interruptible(&fepriv->sem))
                        break;

                if (fepriv->reinitialise) {
                        dvb_frontend_init(fe);
                        if (fepriv->tone != -1) {
                                fe->ops.set_tone(fe, fepriv->tone);
                        }
                        if (fepriv->voltage != -1) {
                                fe->ops.set_voltage(fe, fepriv->voltage);
                        }
                        fepriv->reinitialise = 0;
                }

                /* do an iteration of the tuning loop */
                if (fe->ops.get_frontend_algo) {
                        if (fe->ops.get_frontend_algo(fe) == FE_ALGO_HW) {
                                /* have we been asked to retune? */
                                params = NULL;
                                if (fepriv->state & FESTATE_RETUNE) {
                                        params = &fepriv->parameters;
                                        fepriv->state = FESTATE_TUNED;
                                }

                                fe->ops.tune(fe, params, fepriv->tune_mode_flags, &fepriv->delay, &s);
                                if (s != fepriv->status) {
                                        dvb_frontend_add_event(fe, s);
                                        fepriv->status = s;
                                }
                        } else
                                dvb_frontend_swzigzag(fe);
                } else
                        dvb_frontend_swzigzag(fe);
        }

        if (dvb_shutdown_timeout) {
                if (dvb_powerdown_on_sleep)
                        if (fe->ops.set_voltage)
                                fe->ops.set_voltage(fe, SEC_VOLTAGE_OFF);
                if (fe->ops.tuner_ops.sleep) {
                        fe->ops.tuner_ops.sleep(fe);
                        if (fe->ops.i2c_gate_ctrl)
                                fe->ops.i2c_gate_ctrl(fe, 0);
                }
                if (fe->ops.sleep)
                        fe->ops.sleep(fe);
        }

        fepriv->thread_pid = 0;
        mb();

        dvb_frontend_wakeup(fe);
        return 0;
}

static void dvb_frontend_stop(struct dvb_frontend *fe)
{
        unsigned long ret;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        dprintk ("%s\n", __FUNCTION__);

        fepriv->exit = 1;
        mb();

        if (!fepriv->thread_pid)
                return;

        /* check if the thread is really alive */
        if (kill_proc(fepriv->thread_pid, 0, 1) == -ESRCH) {
                printk("dvb_frontend_stop: thread PID %d already died\n",
                                fepriv->thread_pid);
                /* make sure the mutex was not held by the thread */
                init_MUTEX (&fepriv->sem);
                return;
        }

        /* wake up the frontend thread, so it notices that fe->exit == 1 */
        dvb_frontend_wakeup(fe);

        /* wait until the frontend thread has exited */
        ret = wait_event_interruptible(fepriv->wait_queue,0 == fepriv->thread_pid);
        if (-ERESTARTSYS != ret) {
                fepriv->state = FESTATE_IDLE;
                return;
        }
        fepriv->state = FESTATE_IDLE;

        /* paranoia check in case a signal arrived */
        if (fepriv->thread_pid)
                printk("dvb_frontend_stop: warning: thread PID %d won't exit\n",
                                fepriv->thread_pid);
}

s32 timeval_usec_diff(struct timeval lasttime, struct timeval curtime)
{
        return ((curtime.tv_usec < lasttime.tv_usec) ?
                1000000 - lasttime.tv_usec + curtime.tv_usec :
                curtime.tv_usec - lasttime.tv_usec);
}
EXPORT_SYMBOL(timeval_usec_diff);

static inline void timeval_usec_add(struct timeval *curtime, u32 add_usec)
{
        curtime->tv_usec += add_usec;
        if (curtime->tv_usec >= 1000000) {
                curtime->tv_usec -= 1000000;
                curtime->tv_sec++;
        }
}

/*
 * Sleep until gettimeofday() > waketime + add_usec
 * This needs to be as precise as possible, but as the delay is
 * usually between 2ms and 32ms, it is done using a scheduled msleep
 * followed by usleep (normally a busy-wait loop) for the remainder
 */
void dvb_frontend_sleep_until(struct timeval *waketime, u32 add_usec)
{
        struct timeval lasttime;
        s32 delta, newdelta;

        timeval_usec_add(waketime, add_usec);

        do_gettimeofday(&lasttime);
        delta = timeval_usec_diff(lasttime, *waketime);
        if (delta > 2500) {
                msleep((delta - 1500) / 1000);
                do_gettimeofday(&lasttime);
                newdelta = timeval_usec_diff(lasttime, *waketime);
                delta = (newdelta > delta) ? 0 : newdelta;
        }
        if (delta > 0)
                udelay(delta);
}
EXPORT_SYMBOL(dvb_frontend_sleep_until);

static int dvb_frontend_start(struct dvb_frontend *fe)
{
        int ret;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        dprintk ("%s\n", __FUNCTION__);

        if (fepriv->thread_pid) {
                if (!fepriv->exit)
                        return 0;
                else
                        dvb_frontend_stop (fe);
        }

        if (signal_pending(current))
                return -EINTR;
        if (down_interruptible (&fepriv->sem))
                return -EINTR;

        fepriv->state = FESTATE_IDLE;
        fepriv->exit = 0;
        fepriv->thread_pid = 0;
        mb();

        ret = kernel_thread (dvb_frontend_thread, fe, 0);

        if (ret < 0) {
                printk("dvb_frontend_start: failed to start kernel_thread (%d)\n", ret);
                up(&fepriv->sem);
                return ret;
        }
        fepriv->thread_pid = ret;

        return 0;
}

static int dvb_frontend_ioctl(struct inode *inode, struct file *file,
                        unsigned int cmd, void *parg)
{
        struct dvb_device *dvbdev = file->private_data;
        struct dvb_frontend *fe = dvbdev->priv;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;
        int err = -EOPNOTSUPP;

        dprintk ("%s\n", __FUNCTION__);

        if (!fe || fepriv->exit)
                return -ENODEV;

        if ((file->f_flags & O_ACCMODE) == O_RDONLY &&
            (_IOC_DIR(cmd) != _IOC_READ || cmd == FE_GET_EVENT ||
             cmd == FE_DISEQC_RECV_SLAVE_REPLY))
                return -EPERM;

        if (down_interruptible (&fepriv->sem))
                return -ERESTARTSYS;

        switch (cmd) {
        case FE_GET_INFO: {
                struct dvb_frontend_info* info = parg;
                memcpy(info, &fe->ops.info, sizeof(struct dvb_frontend_info));

                /* Force the CAN_INVERSION_AUTO bit on. If the frontend doesn't
                 * do it, it is done for it. */
                info->caps |= FE_CAN_INVERSION_AUTO;
                err = 0;
                break;
        }

        case FE_READ_STATUS: {
                fe_status_t* status = parg;

                /* if retune was requested but hasn't occured yet, prevent
                 * that user get signal state from previous tuning */
                if(fepriv->state == FESTATE_RETUNE) {
                        err=0;
                        *status = 0;
                        break;
                }

                if (fe->ops.read_status)
                        err = fe->ops.read_status(fe, status);
                break;
        }
        case FE_READ_BER:
                if (fe->ops.read_ber)
                        err = fe->ops.read_ber(fe, (__u32*) parg);
                break;

        case FE_READ_SIGNAL_STRENGTH:
                if (fe->ops.read_signal_strength)
                        err = fe->ops.read_signal_strength(fe, (__u16*) parg);
                break;

        case FE_READ_SNR:
                if (fe->ops.read_snr)
                        err = fe->ops.read_snr(fe, (__u16*) parg);
                break;

        case FE_READ_UNCORRECTED_BLOCKS:
                if (fe->ops.read_ucblocks)
                        err = fe->ops.read_ucblocks(fe, (__u32*) parg);
                break;


        case FE_DISEQC_RESET_OVERLOAD:
                if (fe->ops.diseqc_reset_overload) {
                        err = fe->ops.diseqc_reset_overload(fe);
                        fepriv->state = FESTATE_DISEQC;
                        fepriv->status = 0;
                }
                break;

        case FE_DISEQC_SEND_MASTER_CMD:
                if (fe->ops.diseqc_send_master_cmd) {
                        err = fe->ops.diseqc_send_master_cmd(fe, (struct dvb_diseqc_master_cmd*) parg);
                        fepriv->state = FESTATE_DISEQC;
                        fepriv->status = 0;
                }
                break;

        case FE_DISEQC_SEND_BURST:
                if (fe->ops.diseqc_send_burst) {
                        err = fe->ops.diseqc_send_burst(fe, (fe_sec_mini_cmd_t) parg);
                        fepriv->state = FESTATE_DISEQC;
                        fepriv->status = 0;
                }
                break;

        case FE_SET_TONE:
                if (fe->ops.set_tone) {
                        err = fe->ops.set_tone(fe, (fe_sec_tone_mode_t) parg);
                        fepriv->tone = (fe_sec_tone_mode_t) parg;
                        fepriv->state = FESTATE_DISEQC;
                        fepriv->status = 0;
                }
                break;

        case FE_SET_VOLTAGE:
                if (fe->ops.set_voltage) {
                        err = fe->ops.set_voltage(fe, (fe_sec_voltage_t) parg);
                        fepriv->voltage = (fe_sec_voltage_t) parg;
                        fepriv->state = FESTATE_DISEQC;
                        fepriv->status = 0;
                }
                break;

        case FE_DISHNETWORK_SEND_LEGACY_CMD:
                if (fe->ops.dishnetwork_send_legacy_command) {
                        err = fe->ops.dishnetwork_send_legacy_command(fe, (unsigned long) parg);
                        fepriv->state = FESTATE_DISEQC;
                        fepriv->status = 0;
                } else if (fe->ops.set_voltage) {
                        /*
                         * NOTE: This is a fallback condition.  Some frontends
                         * (stv0299 for instance) take longer than 8msec to
                         * respond to a set_voltage command.  Those switches
                         * need custom routines to switch properly.  For all
                         * other frontends, the following shoule work ok.
                         * Dish network legacy switches (as used by Dish500)
                         * are controlled by sending 9-bit command words
                         * spaced 8msec apart.
                         * the actual command word is switch/port dependant
                         * so it is up to the userspace application to send
                         * the right command.
                         * The command must always start with a '0' after
                         * initialization, so parg is 8 bits and does not
                         * include the initialization or start bit
                         */
                        unsigned long cmd = ((unsigned long) parg) << 1;
                        struct timeval nexttime;
                        struct timeval tv[10];
                        int i;
                        u8 last = 1;
                        if (dvb_frontend_debug)
                                printk("%s switch command: 0x%04lx\n", __FUNCTION__, cmd);
                        do_gettimeofday(&nexttime);
                        if (dvb_frontend_debug)
                                memcpy(&tv[0], &nexttime, sizeof(struct timeval));
                        /* before sending a command, initialize by sending
                         * a 32ms 18V to the switch
                         */
                        fe->ops.set_voltage(fe, SEC_VOLTAGE_18);
                        dvb_frontend_sleep_until(&nexttime, 32000);

                        for (i = 0; i < 9; i++) {
                                if (dvb_frontend_debug)
                                        do_gettimeofday(&tv[i + 1]);
                                if ((cmd & 0x01) != last) {
                                        /* set voltage to (last ? 13V : 18V) */
                                        fe->ops.set_voltage(fe, (last) ? SEC_VOLTAGE_13 : SEC_VOLTAGE_18);
                                        last = (last) ? 0 : 1;
                                }
                                cmd = cmd >> 1;
                                if (i != 8)
                                        dvb_frontend_sleep_until(&nexttime, 8000);
                        }
                        if (dvb_frontend_debug) {
                                printk("%s(%d): switch delay (should be 32k followed by all 8k\n",
                                        __FUNCTION__, fe->dvb->num);
                                for (i = 1; i < 10; i++)
                                        printk("%d: %d\n", i, timeval_usec_diff(tv[i-1] , tv[i]));
                        }
                        err = 0;
                        fepriv->state = FESTATE_DISEQC;
                        fepriv->status = 0;
                }
                break;

        case FE_DISEQC_RECV_SLAVE_REPLY:
                if (fe->ops.diseqc_recv_slave_reply)
                        err = fe->ops.diseqc_recv_slave_reply(fe, (struct dvb_diseqc_slave_reply*) parg);
                break;

        case FE_ENABLE_HIGH_LNB_VOLTAGE:
                if (fe->ops.enable_high_lnb_voltage)
                        err = fe->ops.enable_high_lnb_voltage(fe, (long) parg);
                break;

        case FE_SET_FRONTEND: {
                struct dvb_frontend_tune_settings fetunesettings;

                memcpy (&fepriv->parameters, parg,
                        sizeof (struct dvb_frontend_parameters));

                memset(&fetunesettings, 0, sizeof(struct dvb_frontend_tune_settings));
                memcpy(&fetunesettings.parameters, parg,
                       sizeof (struct dvb_frontend_parameters));

                /* force auto frequency inversion if requested */
                if (dvb_force_auto_inversion) {
                        fepriv->parameters.inversion = INVERSION_AUTO;
                        fetunesettings.parameters.inversion = INVERSION_AUTO;
                }
                if (fe->ops.info.type == FE_OFDM) {
                        /* without hierachical coding code_rate_LP is irrelevant,
                         * so we tolerate the otherwise invalid FEC_NONE setting */
                        if (fepriv->parameters.u.ofdm.hierarchy_information == HIERARCHY_NONE &&
                            fepriv->parameters.u.ofdm.code_rate_LP == FEC_NONE)
                                fepriv->parameters.u.ofdm.code_rate_LP = FEC_AUTO;
                }

                /* get frontend-specific tuning settings */
                if (fe->ops.get_tune_settings && (fe->ops.get_tune_settings(fe, &fetunesettings) == 0)) {
                        fepriv->min_delay = (fetunesettings.min_delay_ms * HZ) / 1000;
                        fepriv->max_drift = fetunesettings.max_drift;
                        fepriv->step_size = fetunesettings.step_size;
                } else {
                        /* default values */
                        switch(fe->ops.info.type) {
                        case FE_QPSK:
                                fepriv->min_delay = HZ/20;
                                fepriv->step_size = fepriv->parameters.u.qpsk.symbol_rate / 16000;
                                fepriv->max_drift = fepriv->parameters.u.qpsk.symbol_rate / 2000;
                                break;

                        case FE_QAM:
                                fepriv->min_delay = HZ/20;
                                fepriv->step_size = 0; /* no zigzag */
                                fepriv->max_drift = 0;
                                break;

                        case FE_OFDM:
                                fepriv->min_delay = HZ/20;
                                fepriv->step_size = fe->ops.info.frequency_stepsize * 2;
                                fepriv->max_drift = (fe->ops.info.frequency_stepsize * 2) + 1;
                                break;
                        case FE_ATSC:
                                fepriv->min_delay = HZ/20;
                                fepriv->step_size = 0;
                                fepriv->max_drift = 0;
                                break;
                        }
                }
                if (dvb_override_tune_delay > 0)
                        fepriv->min_delay = (dvb_override_tune_delay * HZ) / 1000;

                fepriv->state = FESTATE_RETUNE;
                dvb_frontend_wakeup(fe);
                dvb_frontend_add_event(fe, 0);
                fepriv->status = 0;
                err = 0;
                break;
        }

        case FE_GET_EVENT:
                err = dvb_frontend_get_event (fe, parg, file->f_flags);
                break;

        case FE_GET_FRONTEND:
                if (fe->ops.get_frontend) {
                        memcpy (parg, &fepriv->parameters, sizeof (struct dvb_frontend_parameters));
                        err = fe->ops.get_frontend(fe, (struct dvb_frontend_parameters*) parg);
                }
                break;

        case FE_SET_FRONTEND_TUNE_MODE:
                fepriv->tune_mode_flags = (unsigned long) parg;
                err = 0;
                break;
        };

        up (&fepriv->sem);
        return err;
}

static unsigned int dvb_frontend_poll(struct file *file, struct poll_table_struct *wait)
{
        struct dvb_device *dvbdev = file->private_data;
        struct dvb_frontend *fe = dvbdev->priv;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        dprintk ("%s\n", __FUNCTION__);

        poll_wait (file, &fepriv->events.wait_queue, wait);

        if (fepriv->events.eventw != fepriv->events.eventr)
                return (POLLIN | POLLRDNORM | POLLPRI);

        return 0;
}

static int dvb_frontend_open(struct inode *inode, struct file *file)
{
        struct dvb_device *dvbdev = file->private_data;
        struct dvb_frontend *fe = dvbdev->priv;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;
        int ret;

        dprintk ("%s\n", __FUNCTION__);

        if ((ret = dvb_generic_open (inode, file)) < 0)
                return ret;

        if ((file->f_flags & O_ACCMODE) != O_RDONLY) {
                ret = dvb_frontend_start (fe);
                if (ret)
                        dvb_generic_release (inode, file);

                /*  empty event queue */
                fepriv->events.eventr = fepriv->events.eventw = 0;

                /* normal tune mode when opened R/W */
                fepriv->tune_mode_flags &= ~FE_TUNE_MODE_ONESHOT;
                fepriv->tone = -1;
                fepriv->voltage = -1;
        }

        return ret;
}

static int dvb_frontend_release(struct inode *inode, struct file *file)
{
        struct dvb_device *dvbdev = file->private_data;
        struct dvb_frontend *fe = dvbdev->priv;
        struct dvb_frontend_private *fepriv = fe->frontend_priv;

        dprintk ("%s\n", __FUNCTION__);

        if ((file->f_flags & O_ACCMODE) != O_RDONLY)
                fepriv->release_jiffies = jiffies;

        return dvb_generic_release (inode, file);
}

static struct file_operations dvb_frontend_fops = {
        .owner          = THIS_MODULE,
        .ioctl          = dvb_generic_ioctl,
        .poll           = dvb_frontend_poll,
        .open           = dvb_frontend_open,
        .release        = dvb_frontend_release
};

int dvb_register_frontend(struct dvb_adapter* dvb,
                          struct dvb_frontend* fe)
{
        struct dvb_frontend_private *fepriv;
        static const struct dvb_device dvbdev_template = {
                .users = ~0,
                .writers = 1,
                .readers = (~0)-1,
                .fops = &dvb_frontend_fops,
                .kernel_ioctl = dvb_frontend_ioctl
        };

        dprintk ("%s\n", __FUNCTION__);

        if (mutex_lock_interruptible(&frontend_mutex))
                return -ERESTARTSYS;

        fe->frontend_priv = kzalloc(sizeof(struct dvb_frontend_private), GFP_KERNEL);
        if (fe->frontend_priv == NULL) {
                mutex_unlock(&frontend_mutex);
                return -ENOMEM;
        }
        fepriv = fe->frontend_priv;

        init_MUTEX (&fepriv->sem);
        init_waitqueue_head (&fepriv->wait_queue);
        init_waitqueue_head (&fepriv->events.wait_queue);
        init_MUTEX (&fepriv->events.sem);
        fe->dvb = dvb;
        fepriv->inversion = INVERSION_OFF;

        printk ("DVB: registering frontend %i (%s)...\n",
                fe->dvb->num,
                fe->ops.info.name);

        dvb_register_device (fe->dvb, &fepriv->dvbdev, &dvbdev_template,
                             fe, DVB_DEVICE_FRONTEND);

        mutex_unlock(&frontend_mutex);
        return 0;
}
EXPORT_SYMBOL(dvb_register_frontend);

int dvb_unregister_frontend(struct dvb_frontend* fe)
{
        struct dvb_frontend_private *fepriv = fe->frontend_priv;
        dprintk ("%s\n", __FUNCTION__);

        mutex_lock(&frontend_mutex);
        dvb_unregister_device (fepriv->dvbdev);
        dvb_frontend_stop (fe);
        if (fe->ops.tuner_ops.release) {
                fe->ops.tuner_ops.release(fe);
                if (fe->ops.i2c_gate_ctrl)
                        fe->ops.i2c_gate_ctrl(fe, 0);
        }
        if (fe->ops.release)
                fe->ops.release(fe);
        else
                printk("dvb_frontend: Demodulator (%s) does not have a release callback!\n", fe->ops.info.name);
        /* fe is invalid now */
        kfree(fepriv);
        mutex_unlock(&frontend_mutex);
        return 0;
}
EXPORT_SYMBOL(dvb_unregister_frontend);