/*
 * Parallel-port resource manager code.
 *
 * Authors: David Campbell <campbell@tirian.che.curtin.edu.au>
 *          Tim Waugh <tim@cyberelk.demon.co.uk>
 *          Jose Renau <renau@acm.org>
 *          Philip Blundell <philb@gnu.org>
 *          Andrea Arcangeli
 *
 * based on work by Grant Guenther <grant@torque.net>
 *          and Philip Blundell
 *
 * Any part of this program may be used in documents licensed under
 * the GNU Free Documentation License, Version 1.1 or any later version
 * published by the Free Software Foundation.
 */

#undef PARPORT_DEBUG_SHARING            /* undef for production */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/threads.h>
#include <linux/parport.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/kmod.h>
#include <linux/device.h>

#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <asm/irq.h>

#undef PARPORT_PARANOID

#define PARPORT_DEFAULT_TIMESLICE       (HZ/5)

unsigned long parport_default_timeslice = PARPORT_DEFAULT_TIMESLICE;
int parport_default_spintime =  DEFAULT_SPIN_TIME;

static LIST_HEAD(portlist);
static DEFINE_SPINLOCK(parportlist_lock);

/* list of all allocated ports, sorted by ->number */
static LIST_HEAD(all_ports);
static DEFINE_SPINLOCK(full_list_lock);

static DEFINE_MUTEX(registration_lock);

/* What you can do to a port that's gone away.. */
static void dead_write_lines(struct parport *p, unsigned char b){}
static unsigned char dead_read_lines(struct parport *p) { return 0; }
static unsigned char dead_frob_lines(struct parport *p, unsigned char b,
                             unsigned char c) { return 0; }
static void dead_onearg(struct parport *p){}
static void dead_initstate(struct pardevice *d, struct parport_state *s) { }
static void dead_state(struct parport *p, struct parport_state *s) { }
static size_t dead_write(struct parport *p, const void *b, size_t l, int f)
{ return 0; }
static size_t dead_read(struct parport *p, void *b, size_t l, int f)
{ return 0; }
static struct parport_operations dead_ops = {
        .write_data     = dead_write_lines,     /* data */
        .read_data      = dead_read_lines,

        .write_control  = dead_write_lines,     /* control */
        .read_control   = dead_read_lines,
        .frob_control   = dead_frob_lines,

        .read_status    = dead_read_lines,      /* status */

        .enable_irq     = dead_onearg,          /* enable_irq */
        .disable_irq    = dead_onearg,          /* disable_irq */

        .data_forward   = dead_onearg,          /* data_forward */
        .data_reverse   = dead_onearg,          /* data_reverse */

        .init_state     = dead_initstate,       /* init_state */
        .save_state     = dead_state,
        .restore_state  = dead_state,

        .epp_write_data = dead_write,           /* epp */
        .epp_read_data  = dead_read,
        .epp_write_addr = dead_write,
        .epp_read_addr  = dead_read,

        .ecp_write_data = dead_write,           /* ecp */
        .ecp_read_data  = dead_read,
        .ecp_write_addr = dead_write,

        .compat_write_data      = dead_write,   /* compat */
        .nibble_read_data       = dead_read,    /* nibble */
        .byte_read_data         = dead_read,    /* byte */

        .owner          = NULL,
};

static struct device_type parport_device_type = {
        .name = "parport",
};

static int is_parport(struct device *dev)
{
        return dev->type == &parport_device_type;
}

static int parport_probe(struct device *dev)
{
        struct parport_driver *drv;

        if (is_parport(dev))
                return -ENODEV;

        drv = to_parport_driver(dev->driver);
        if (!drv->probe) {
                /* if driver has not defined a custom probe */
                struct pardevice *par_dev = to_pardevice(dev);

                if (strcmp(par_dev->name, drv->name))
                        return -ENODEV;
                return 0;
        }
        /* if driver defined its own probe */
        return drv->probe(to_pardevice(dev));
}

static const struct bus_type parport_bus_type = {
        .name = "parport",
        .probe = parport_probe,
};

int parport_bus_init(void)
{
        return bus_register(&parport_bus_type);
}

void parport_bus_exit(void)
{
        bus_unregister(&parport_bus_type);
}

/*
 * iterates through all the drivers registered with the bus and sends the port
 * details to the match_port callback of the driver, so that the driver can
 * know about the new port that just registered with the bus and decide if it
 * wants to use this new port.
 */
static int driver_check(struct device_driver *dev_drv, void *_port)
{
        struct parport *port = _port;
        struct parport_driver *drv = to_parport_driver(dev_drv);

        if (drv->match_port)
                drv->match_port(port);
        return 0;
}

/* Call attach(port) for each registered driver. */
static void attach_driver_chain(struct parport *port)
{
        /* caller has exclusive registration_lock */

        /*
         * call the driver_check function of the drivers registered in
         * new device model
         */

        bus_for_each_drv(&parport_bus_type, NULL, port, driver_check);
}

static int driver_detach(struct device_driver *_drv, void *_port)
{
        struct parport *port = _port;
        struct parport_driver *drv = to_parport_driver(_drv);

        if (drv->detach)
                drv->detach(port);
        return 0;
}

/* Call detach(port) for each registered driver. */
static void detach_driver_chain(struct parport *port)
{
        /* caller has exclusive registration_lock */

        /*
         * call the detach function of the drivers registered in
         * new device model
         */

        bus_for_each_drv(&parport_bus_type, NULL, port, driver_detach);
}

/* Ask kmod for some lowlevel drivers. */
static void get_lowlevel_driver(void)
{
        /*
         * There is no actual module called this: you should set
         * up an alias for modutils.
         */
        request_module("parport_lowlevel");
}

/*
 * iterates through all the devices connected to the bus and sends the device
 * details to the match_port callback of the driver, so that the driver can
 * know what are all the ports that are connected to the bus and choose the
 * port to which it wants to register its device.
 */
static int port_check(struct device *dev, void *dev_drv)
{
        struct parport_driver *drv = dev_drv;

        /* only send ports, do not send other devices connected to bus */
        if (is_parport(dev))
                drv->match_port(to_parport_dev(dev));
        return 0;
}

/*
 * Iterates through all the devices connected to the bus and return 1
 * if the device is a parallel port.
 */

static int port_detect(struct device *dev, void *dev_drv)
{
        if (is_parport(dev))
                return 1;
        return 0;
}

/**
 *      __parport_register_driver - register a parallel port device driver
 *      @drv: structure describing the driver
 *      @owner: owner module of drv
 *      @mod_name: module name string
 *
 *      This can be called by a parallel port device driver in order
 *      to receive notifications about ports being found in the
 *      system, as well as ports no longer available.
 *
 *      If devmodel is true then the new device model is used
 *      for registration.
 *
 *      The @drv structure is allocated by the caller and must not be
 *      deallocated until after calling parport_unregister_driver().
 *
 *      If using the non device model:
 *      The driver's attach() function may block.  The port that
 *      attach() is given will be valid for the duration of the
 *      callback, but if the driver wants to take a copy of the
 *      pointer it must call parport_get_port() to do so.  Calling
 *      parport_register_device() on that port will do this for you.
 *
 *      The driver's detach() function may block.  The port that
 *      detach() is given will be valid for the duration of the
 *      callback, but if the driver wants to take a copy of the
 *      pointer it must call parport_get_port() to do so.
 *
 *
 *      Returns 0 on success. The non device model will always succeeds.
 *      but the new device model can fail and will return the error code.
 **/

int __parport_register_driver(struct parport_driver *drv, struct module *owner,
                              const char *mod_name)
{
        /* using device model */
        int ret;

        /* initialize common driver fields */
        drv->driver.name = drv->name;
        drv->driver.bus = &parport_bus_type;
        drv->driver.owner = owner;
        drv->driver.mod_name = mod_name;
        ret = driver_register(&drv->driver);
        if (ret)
                return ret;

        /*
         * check if bus has any parallel port registered, if
         * none is found then load the lowlevel driver.
         */
        ret = bus_for_each_dev(&parport_bus_type, NULL, NULL,
                               port_detect);
        if (!ret)
                get_lowlevel_driver();

        mutex_lock(&registration_lock);
        if (drv->match_port)
                bus_for_each_dev(&parport_bus_type, NULL, drv,
                                 port_check);
        mutex_unlock(&registration_lock);

        return 0;
}
EXPORT_SYMBOL(__parport_register_driver);

static int port_detach(struct device *dev, void *_drv)
{
        struct parport_driver *drv = _drv;

        if (is_parport(dev) && drv->detach)
                drv->detach(to_parport_dev(dev));

        return 0;
}

/**
 *      parport_unregister_driver - deregister a parallel port device driver
 *      @drv: structure describing the driver that was given to
 *            parport_register_driver()
 *
 *      This should be called by a parallel port device driver that
 *      has registered itself using parport_register_driver() when it
 *      is about to be unloaded.
 *
 *      When it returns, the driver's attach() routine will no longer
 *      be called, and for each port that attach() was called for, the
 *      detach() routine will have been called.
 *
 *      All the driver's attach() and detach() calls are guaranteed to have
 *      finished by the time this function returns.
 **/

void parport_unregister_driver(struct parport_driver *drv)
{
        mutex_lock(&registration_lock);
        bus_for_each_dev(&parport_bus_type, NULL, drv, port_detach);
        driver_unregister(&drv->driver);
        mutex_unlock(&registration_lock);
}
EXPORT_SYMBOL(parport_unregister_driver);

static void free_port(struct device *dev)
{
        int d;
        struct parport *port = to_parport_dev(dev);

        spin_lock(&full_list_lock);
        list_del(&port->full_list);
        spin_unlock(&full_list_lock);
        for (d = 0; d < 5; d++) {
                kfree(port->probe_info[d].class_name);
                kfree(port->probe_info[d].mfr);
                kfree(port->probe_info[d].model);
                kfree(port->probe_info[d].cmdset);
                kfree(port->probe_info[d].description);
        }

        kfree(port);
}

/**
 *      parport_get_port - increment a port's reference count
 *      @port: the port
 *
 *      This ensures that a struct parport pointer remains valid
 *      until the matching parport_put_port() call.
 **/

struct parport *parport_get_port(struct parport *port)
{
        struct device *dev = get_device(&port->bus_dev);

        return to_parport_dev(dev);
}
EXPORT_SYMBOL(parport_get_port);

void parport_del_port(struct parport *port)
{
        device_unregister(&port->bus_dev);
}
EXPORT_SYMBOL(parport_del_port);

/**
 *      parport_put_port - decrement a port's reference count
 *      @port: the port
 *
 *      This should be called once for each call to parport_get_port(),
 *      once the port is no longer needed. When the reference count reaches
 *      zero (port is no longer used), free_port is called.
 **/

void parport_put_port(struct parport *port)
{
        put_device(&port->bus_dev);
}
EXPORT_SYMBOL(parport_put_port);

/**
 *      parport_register_port - register a parallel port
 *      @base: base I/O address
 *      @irq: IRQ line
 *      @dma: DMA channel
 *      @ops: pointer to the port driver's port operations structure
 *
 *      When a parallel port (lowlevel) driver finds a port that
 *      should be made available to parallel port device drivers, it
 *      should call parport_register_port().  The @base, @irq, and
 *      @dma parameters are for the convenience of port drivers, and
 *      for ports where they aren't meaningful needn't be set to
 *      anything special.  They can be altered afterwards by adjusting
 *      the relevant members of the parport structure that is returned
 *      and represents the port.  They should not be tampered with
 *      after calling parport_announce_port, however.
 *
 *      If there are parallel port device drivers in the system that
 *      have registered themselves using parport_register_driver(),
 *      they are not told about the port at this time; that is done by
 *      parport_announce_port().
 *
 *      The @ops structure is allocated by the caller, and must not be
 *      deallocated before calling parport_remove_port().
 *
 *      If there is no memory to allocate a new parport structure,
 *      this function will return %NULL.
 **/

struct parport *parport_register_port(unsigned long base, int irq, int dma,
                                      struct parport_operations *ops)
{
        struct list_head *l;
        struct parport *tmp;
        int num;
        int device;
        int ret;

        tmp = kzalloc_obj(struct parport);
        if (!tmp)
                return NULL;

        /* Init our structure */
        tmp->base = base;
        tmp->irq = irq;
        tmp->dma = dma;
        tmp->muxport = tmp->daisy = tmp->muxsel = -1;
        INIT_LIST_HEAD(&tmp->list);
        tmp->ops = ops;
        tmp->physport = tmp;
        rwlock_init(&tmp->cad_lock);
        spin_lock_init(&tmp->waitlist_lock);
        spin_lock_init(&tmp->pardevice_lock);
        tmp->ieee1284.mode = IEEE1284_MODE_COMPAT;
        tmp->ieee1284.phase = IEEE1284_PH_FWD_IDLE;
        sema_init(&tmp->ieee1284.irq, 0);
        tmp->spintime = parport_default_spintime;
        atomic_set(&tmp->ref_count, 1);

        /* Search for the lowest free parport number. */

        spin_lock(&full_list_lock);
        num = 0;
        list_for_each(l, &all_ports) {
                struct parport *p = list_entry(l, struct parport, full_list);

                if (p->number != num++)
                        break;
        }
        tmp->portnum = tmp->number = num;
        list_add_tail(&tmp->full_list, l);
        spin_unlock(&full_list_lock);

        /*
         * Now that the portnum is known finish doing the Init.
         */
        dev_set_name(&tmp->bus_dev, "parport%d", tmp->portnum);
        tmp->bus_dev.bus = &parport_bus_type;
        tmp->bus_dev.release = free_port;
        tmp->bus_dev.type = &parport_device_type;

        tmp->name = dev_name(&tmp->bus_dev);

        for (device = 0; device < 5; device++)
                /* assume the worst */
                tmp->probe_info[device].class = PARPORT_CLASS_LEGACY;

        ret = device_register(&tmp->bus_dev);
        if (ret) {
                put_device(&tmp->bus_dev);
                return NULL;
        }

        return tmp;
}
EXPORT_SYMBOL(parport_register_port);

/**
 *      parport_announce_port - tell device drivers about a parallel port
 *      @port: parallel port to announce
 *
 *      After a port driver has registered a parallel port with
 *      parport_register_port, and performed any necessary
 *      initialisation or adjustments, it should call
 *      parport_announce_port() in order to notify all device drivers
 *      that have called parport_register_driver().  Their attach()
 *      functions will be called, with @port as the parameter.
 **/

void parport_announce_port(struct parport *port)
{
        int i;

#ifdef CONFIG_PARPORT_1284
        /* Analyse the IEEE1284.3 topology of the port. */
        parport_daisy_init(port);
#endif

        if (!port->dev)
                pr_warn("%s: fix this legacy no-device port driver!\n",
                        port->name);

        parport_proc_register(port);
        mutex_lock(&registration_lock);
        spin_lock_irq(&parportlist_lock);
        list_add_tail(&port->list, &portlist);
        for (i = 1; i < 3; i++) {
                struct parport *slave = port->slaves[i-1];
                if (slave)
                        list_add_tail(&slave->list, &portlist);
        }
        spin_unlock_irq(&parportlist_lock);

        /* Let drivers know that new port(s) has arrived. */
        attach_driver_chain(port);
        for (i = 1; i < 3; i++) {
                struct parport *slave = port->slaves[i-1];
                if (slave)
                        attach_driver_chain(slave);
        }
        mutex_unlock(&registration_lock);
}
EXPORT_SYMBOL(parport_announce_port);

/**
 *      parport_remove_port - deregister a parallel port
 *      @port: parallel port to deregister
 *
 *      When a parallel port driver is forcibly unloaded, or a
 *      parallel port becomes inaccessible, the port driver must call
 *      this function in order to deal with device drivers that still
 *      want to use it.
 *
 *      The parport structure associated with the port has its
 *      operations structure replaced with one containing 'null'
 *      operations that return errors or just don't do anything.
 *
 *      Any drivers that have registered themselves using
 *      parport_register_driver() are notified that the port is no
 *      longer accessible by having their detach() routines called
 *      with @port as the parameter.
 **/

void parport_remove_port(struct parport *port)
{
        int i;

        mutex_lock(&registration_lock);

        /* Spread the word. */
        detach_driver_chain(port);

#ifdef CONFIG_PARPORT_1284
        /* Forget the IEEE1284.3 topology of the port. */
        parport_daisy_fini(port);
        for (i = 1; i < 3; i++) {
                struct parport *slave = port->slaves[i-1];
                if (!slave)
                        continue;
                detach_driver_chain(slave);
                parport_daisy_fini(slave);
        }
#endif

        port->ops = &dead_ops;
        spin_lock(&parportlist_lock);
        list_del_init(&port->list);
        for (i = 1; i < 3; i++) {
                struct parport *slave = port->slaves[i-1];
                if (slave)
                        list_del_init(&slave->list);
        }
        spin_unlock(&parportlist_lock);

        mutex_unlock(&registration_lock);

        parport_proc_unregister(port);

        for (i = 1; i < 3; i++) {
                struct parport *slave = port->slaves[i-1];
                if (slave)
                        parport_put_port(slave);
        }
}
EXPORT_SYMBOL(parport_remove_port);

static void free_pardevice(struct device *dev)
{
        struct pardevice *par_dev = to_pardevice(dev);

        kfree_const(par_dev->name);
        kfree(par_dev);
}

/**
 *      parport_register_dev_model - register a device on a parallel port
 *      @port: port to which the device is attached
 *      @name: a name to refer to the device
 *      @par_dev_cb: struct containing callbacks
 *      @id: device number to be given to the device
 *
 *      This function, called by parallel port device drivers,
 *      declares that a device is connected to a port, and tells the
 *      system all it needs to know.
 *
 *      The struct pardev_cb contains pointer to callbacks. preemption
 *      callback function, @preempt, is called when this device driver
 *      has claimed access to the port but another device driver wants
 *      to use it.  It is given, @private, as its parameter, and should
 *      return zero if it is willing for the system to release the port
 *      to another driver on its behalf. If it wants to keep control of
 *      the port it should return non-zero, and no action will be taken.
 *      It is good manners for the driver to try to release the port at
 *      the earliest opportunity after its preemption callback rejects a
 *      preemption attempt. Note that if a preemption callback is happy
 *      for preemption to go ahead, there is no need to release the
 *      port; it is done automatically. This function may not block, as
 *      it may be called from interrupt context. If the device driver
 *      does not support preemption, @preempt can be %NULL.
 *
 *      The wake-up ("kick") callback function, @wakeup, is called when
 *      the port is available to be claimed for exclusive access; that
 *      is, parport_claim() is guaranteed to succeed when called from
 *      inside the wake-up callback function.  If the driver wants to
 *      claim the port it should do so; otherwise, it need not take
 *      any action.  This function may not block, as it may be called
 *      from interrupt context.  If the device driver does not want to
 *      be explicitly invited to claim the port in this way, @wakeup can
 *      be %NULL.
 *
 *      The interrupt handler, @irq_func, is called when an interrupt
 *      arrives from the parallel port.  Note that if a device driver
 *      wants to use interrupts it should use parport_enable_irq(),
 *      and can also check the irq member of the parport structure
 *      representing the port.
 *
 *      The parallel port (lowlevel) driver is the one that has called
 *      request_irq() and whose interrupt handler is called first.
 *      This handler does whatever needs to be done to the hardware to
 *      acknowledge the interrupt (for PC-style ports there is nothing
 *      special to be done).  It then tells the IEEE 1284 code about
 *      the interrupt, which may involve reacting to an IEEE 1284
 *      event depending on the current IEEE 1284 phase.  After this,
 *      it calls @irq_func.  Needless to say, @irq_func will be called
 *      from interrupt context, and may not block.
 *
 *      The %PARPORT_DEV_EXCL flag is for preventing port sharing, and
 *      so should only be used when sharing the port with other device
 *      drivers is impossible and would lead to incorrect behaviour.
 *      Use it sparingly!  Normally, @flags will be zero.
 *
 *      This function returns a pointer to a structure that represents
 *      the device on the port, or %NULL if there is not enough memory
 *      to allocate space for that structure.
 **/

struct pardevice *
parport_register_dev_model(struct parport *port, const char *name,
                           const struct pardev_cb *par_dev_cb, int id)
{
        struct pardevice *par_dev;
        const char *devname;
        int ret;

        if (port->physport->flags & PARPORT_FLAG_EXCL) {
                /* An exclusive device is registered. */
                pr_err("%s: no more devices allowed\n", port->name);
                return NULL;
        }

        if (par_dev_cb->flags & PARPORT_DEV_LURK) {
                if (!par_dev_cb->preempt || !par_dev_cb->wakeup) {
                        pr_info("%s: refused to register lurking device (%s) without callbacks\n",
                                port->name, name);
                        return NULL;
                }
        }

        if (par_dev_cb->flags & PARPORT_DEV_EXCL) {
                if (port->physport->devices) {
                        /*
                         * If a device is already registered and this new
                         * device wants exclusive access, then no need to
                         * continue as we can not grant exclusive access to
                         * this device.
                         */
                        pr_err("%s: cannot grant exclusive access for device %s\n",
                               port->name, name);
                        return NULL;
                }
        }

        if (!try_module_get(port->ops->owner))
                return NULL;

        parport_get_port(port);

        par_dev = kzalloc_obj(*par_dev);
        if (!par_dev)
                goto err_put_port;

        par_dev->state = kzalloc_obj(*par_dev->state);
        if (!par_dev->state)
                goto err_put_par_dev;

        devname = kstrdup_const(name, GFP_KERNEL);
        if (!devname)
                goto err_free_par_dev;

        par_dev->name = devname;
        par_dev->port = port;
        par_dev->daisy = -1;
        par_dev->preempt = par_dev_cb->preempt;
        par_dev->wakeup = par_dev_cb->wakeup;
        par_dev->private = par_dev_cb->private;
        par_dev->flags = par_dev_cb->flags;
        par_dev->irq_func = par_dev_cb->irq_func;
        par_dev->waiting = 0;
        par_dev->timeout = 5 * HZ;

        par_dev->dev.parent = &port->bus_dev;
        par_dev->dev.bus = &parport_bus_type;
        ret = dev_set_name(&par_dev->dev, "%s.%d", devname, id);
        if (ret)
                goto err_free_devname;
        par_dev->dev.release = free_pardevice;
        par_dev->devmodel = true;
        ret = device_register(&par_dev->dev);
        if (ret) {
                kfree(par_dev->state);
                put_device(&par_dev->dev);
                goto err_put_port;
        }

        /* Chain this onto the list */
        par_dev->prev = NULL;
        /*
         * This function must not run from an irq handler so we don' t need
         * to clear irq on the local CPU. -arca
         */
        spin_lock(&port->physport->pardevice_lock);

        if (par_dev_cb->flags & PARPORT_DEV_EXCL) {
                if (port->physport->devices) {
                        spin_unlock(&port->physport->pardevice_lock);
                        pr_debug("%s: cannot grant exclusive access for device %s\n",
                                 port->name, name);
                        kfree(par_dev->state);
                        device_unregister(&par_dev->dev);
                        goto err_put_port;
                }
                port->flags |= PARPORT_FLAG_EXCL;
        }

        par_dev->next = port->physport->devices;
        wmb();  /*
                 * Make sure that tmp->next is written before it's
                 * added to the list; see comments marked 'no locking
                 * required'
                 */
        if (port->physport->devices)
                port->physport->devices->prev = par_dev;
        port->physport->devices = par_dev;
        spin_unlock(&port->physport->pardevice_lock);

        init_waitqueue_head(&par_dev->wait_q);
        par_dev->timeslice = parport_default_timeslice;
        par_dev->waitnext = NULL;
        par_dev->waitprev = NULL;

        /*
         * This has to be run as last thing since init_state may need other
         * pardevice fields. -arca
         */
        port->ops->init_state(par_dev, par_dev->state);
        if (!test_and_set_bit(PARPORT_DEVPROC_REGISTERED, &port->devflags)) {
                port->proc_device = par_dev;
                parport_device_proc_register(par_dev);
        }

        return par_dev;

err_free_devname:
        kfree_const(devname);
err_free_par_dev:
        kfree(par_dev->state);
err_put_par_dev:
        if (!par_dev->devmodel)
                kfree(par_dev);
err_put_port:
        parport_put_port(port);
        module_put(port->ops->owner);

        return NULL;
}
EXPORT_SYMBOL(parport_register_dev_model);

/**
 *      parport_unregister_device - deregister a device on a parallel port
 *      @dev: pointer to structure representing device
 *
 *      This undoes the effect of parport_register_device().
 **/

void parport_unregister_device(struct pardevice *dev)
{
        struct parport *port;

#ifdef PARPORT_PARANOID
        if (!dev) {
                pr_err("%s: passed NULL\n", __func__);
                return;
        }
#endif

        port = dev->port->physport;

        if (port->proc_device == dev) {
                port->proc_device = NULL;
                clear_bit(PARPORT_DEVPROC_REGISTERED, &port->devflags);
                parport_device_proc_unregister(dev);
        }

        if (port->cad == dev) {
                printk(KERN_DEBUG "%s: %s forgot to release port\n",
                       port->name, dev->name);
                parport_release(dev);
        }

        spin_lock(&port->pardevice_lock);
        if (dev->next)
                dev->next->prev = dev->prev;
        if (dev->prev)
                dev->prev->next = dev->next;
        else
                port->devices = dev->next;

        if (dev->flags & PARPORT_DEV_EXCL)
                port->flags &= ~PARPORT_FLAG_EXCL;

        spin_unlock(&port->pardevice_lock);

        /*
         * Make sure we haven't left any pointers around in the wait
         * list.
         */
        spin_lock_irq(&port->waitlist_lock);
        if (dev->waitprev || dev->waitnext || port->waithead == dev) {
                if (dev->waitprev)
                        dev->waitprev->waitnext = dev->waitnext;
                else
                        port->waithead = dev->waitnext;
                if (dev->waitnext)
                        dev->waitnext->waitprev = dev->waitprev;
                else
                        port->waittail = dev->waitprev;
        }
        spin_unlock_irq(&port->waitlist_lock);

        kfree(dev->state);
        device_unregister(&dev->dev);

        module_put(port->ops->owner);
        parport_put_port(port);
}
EXPORT_SYMBOL(parport_unregister_device);

/**
 *      parport_find_number - find a parallel port by number
 *      @number: parallel port number
 *
 *      This returns the parallel port with the specified number, or
 *      %NULL if there is none.
 *
 *      There is an implicit parport_get_port() done already; to throw
 *      away the reference to the port that parport_find_number()
 *      gives you, use parport_put_port().
 */

struct parport *parport_find_number(int number)
{
        struct parport *port, *result = NULL;

        if (list_empty(&portlist))
                get_lowlevel_driver();

        spin_lock(&parportlist_lock);
        list_for_each_entry(port, &portlist, list) {
                if (port->number == number) {
                        result = parport_get_port(port);
                        break;
                }
        }
        spin_unlock(&parportlist_lock);
        return result;
}
EXPORT_SYMBOL(parport_find_number);

/**
 *      parport_find_base - find a parallel port by base address
 *      @base: base I/O address
 *
 *      This returns the parallel port with the specified base
 *      address, or %NULL if there is none.
 *
 *      There is an implicit parport_get_port() done already; to throw
 *      away the reference to the port that parport_find_base()
 *      gives you, use parport_put_port().
 */

struct parport *parport_find_base(unsigned long base)
{
        struct parport *port, *result = NULL;

        if (list_empty(&portlist))
                get_lowlevel_driver();

        spin_lock(&parportlist_lock);
        list_for_each_entry(port, &portlist, list) {
                if (port->base == base) {
                        result = parport_get_port(port);
                        break;
                }
        }
        spin_unlock(&parportlist_lock);
        return result;
}
EXPORT_SYMBOL(parport_find_base);

/**
 *      parport_claim - claim access to a parallel port device
 *      @dev: pointer to structure representing a device on the port
 *
 *      This function will not block and so can be used from interrupt
 *      context.  If parport_claim() succeeds in claiming access to
 *      the port it returns zero and the port is available to use.  It
 *      may fail (returning non-zero) if the port is in use by another
 *      driver and that driver is not willing to relinquish control of
 *      the port.
 **/

int parport_claim(struct pardevice *dev)
{
        struct pardevice *oldcad;
        struct parport *port = dev->port->physport;
        unsigned long flags;

        if (port->cad == dev) {
                pr_info("%s: %s already owner\n", dev->port->name, dev->name);
                return 0;
        }

        /* Preempt any current device */
        write_lock_irqsave(&port->cad_lock, flags);
        oldcad = port->cad;
        if (oldcad) {
                if (oldcad->preempt) {
                        if (oldcad->preempt(oldcad->private))
                                goto blocked;
                        port->ops->save_state(port, dev->state);
                } else
                        goto blocked;

                if (port->cad != oldcad) {
                        /*
                         * I think we'll actually deadlock rather than
                         * get here, but just in case..
                         */
                        pr_warn("%s: %s released port when preempted!\n",
                                port->name, oldcad->name);
                        if (port->cad)
                                goto blocked;
                }
        }

        /* Can't fail from now on, so mark ourselves as no longer waiting.  */
        if (dev->waiting & 1) {
                dev->waiting = 0;

                /* Take ourselves out of the wait list again.  */
                spin_lock_irq(&port->waitlist_lock);
                if (dev->waitprev)
                        dev->waitprev->waitnext = dev->waitnext;
                else
                        port->waithead = dev->waitnext;
                if (dev->waitnext)
                        dev->waitnext->waitprev = dev->waitprev;
                else
                        port->waittail = dev->waitprev;
                spin_unlock_irq(&port->waitlist_lock);
                dev->waitprev = dev->waitnext = NULL;
        }

        /* Now we do the change of devices */
        port->cad = dev;

#ifdef CONFIG_PARPORT_1284
        /* If it's a mux port, select it. */
        if (dev->port->muxport >= 0) {
                /* FIXME */
                port->muxsel = dev->port->muxport;
        }

        /* If it's a daisy chain device, select it. */
        if (dev->daisy >= 0) {
                /* This could be lazier. */
                if (!parport_daisy_select(port, dev->daisy,
                                           IEEE1284_MODE_COMPAT))
                        port->daisy = dev->daisy;
        }
#endif /* IEEE1284.3 support */

        /* Restore control registers */
        port->ops->restore_state(port, dev->state);
        write_unlock_irqrestore(&port->cad_lock, flags);
        dev->time = jiffies;
        return 0;

blocked:
        /*
         * If this is the first time we tried to claim the port, register an
         * interest.  This is only allowed for devices sleeping in
         * parport_claim_or_block(), or those with a wakeup function.
         */

        /* The cad_lock is still held for writing here */
        if (dev->waiting & 2 || dev->wakeup) {
                spin_lock(&port->waitlist_lock);
                if (test_and_set_bit(0, &dev->waiting) == 0) {
                        /* First add ourselves to the end of the wait list. */
                        dev->waitnext = NULL;
                        dev->waitprev = port->waittail;
                        if (port->waittail) {
                                port->waittail->waitnext = dev;
                                port->waittail = dev;
                        } else
                                port->waithead = port->waittail = dev;
                }
                spin_unlock(&port->waitlist_lock);
        }
        write_unlock_irqrestore(&port->cad_lock, flags);
        return -EAGAIN;
}
EXPORT_SYMBOL(parport_claim);

/**
 *      parport_claim_or_block - claim access to a parallel port device
 *      @dev: pointer to structure representing a device on the port
 *
 *      This behaves like parport_claim(), but will block if necessary
 *      to wait for the port to be free.  A return value of 1
 *      indicates that it slept; 0 means that it succeeded without
 *      needing to sleep.  A negative error code indicates failure.
 **/

int parport_claim_or_block(struct pardevice *dev)
{
        int r;

        /*
         * Signal to parport_claim() that we can wait even without a
         * wakeup function.
         */
        dev->waiting = 2;

        /* Try to claim the port.  If this fails, we need to sleep.  */
        r = parport_claim(dev);
        if (r == -EAGAIN) {
#ifdef PARPORT_DEBUG_SHARING
                printk(KERN_DEBUG "%s: parport_claim() returned -EAGAIN\n",
                       dev->name);
#endif
                /*
                 * FIXME!!! Use the proper locking for dev->waiting,
                 * and make this use the "wait_event_interruptible()"
                 * interfaces. The cli/sti that used to be here
                 * did nothing.
                 *
                 * See also parport_release()
                 */

                /*
                 * If dev->waiting is clear now, an interrupt
                 * gave us the port and we would deadlock if we slept.
                 */
                if (dev->waiting) {
                        wait_event_interruptible(dev->wait_q,
                                                 !dev->waiting);
                        if (signal_pending(current))
                                return -EINTR;
                        r = 1;
                } else {
                        r = 0;
#ifdef PARPORT_DEBUG_SHARING
                        printk(KERN_DEBUG "%s: didn't sleep in parport_claim_or_block()\n",
                               dev->name);
#endif
                }

#ifdef PARPORT_DEBUG_SHARING
                if (dev->port->physport->cad != dev)
                        printk(KERN_DEBUG "%s: exiting parport_claim_or_block but %s owns port!\n",
                               dev->name, dev->port->physport->cad ?
                               dev->port->physport->cad->name : "nobody");
#endif
        }
        dev->waiting = 0;
        return r;
}
EXPORT_SYMBOL(parport_claim_or_block);

/**
 *      parport_release - give up access to a parallel port device
 *      @dev: pointer to structure representing parallel port device
 *
 *      This function cannot fail, but it should not be called without
 *      the port claimed.  Similarly, if the port is already claimed
 *      you should not try claiming it again.
 **/

void parport_release(struct pardevice *dev)
{
        struct parport *port = dev->port->physport;
        struct pardevice *pd;
        unsigned long flags;

        /* Make sure that dev is the current device */
        write_lock_irqsave(&port->cad_lock, flags);
        if (port->cad != dev) {
                write_unlock_irqrestore(&port->cad_lock, flags);
                pr_warn("%s: %s tried to release parport when not owner\n",
                        port->name, dev->name);
                return;
        }

#ifdef CONFIG_PARPORT_1284
        /* If this is on a mux port, deselect it. */
        if (dev->port->muxport >= 0) {
                /* FIXME */
                port->muxsel = -1;
        }

        /* If this is a daisy device, deselect it. */
        if (dev->daisy >= 0) {
                parport_daisy_deselect_all(port);
                port->daisy = -1;
        }
#endif

        port->cad = NULL;
        write_unlock_irqrestore(&port->cad_lock, flags);

        /* Save control registers */
        port->ops->save_state(port, dev->state);

        /*
         * If anybody is waiting, find out who's been there longest and
         * then wake them up. (Note: no locking required)
         */
        /* !!! LOCKING IS NEEDED HERE */
        for (pd = port->waithead; pd; pd = pd->waitnext) {
                if (pd->waiting & 2) { /* sleeping in claim_or_block */
                        parport_claim(pd);
                        if (waitqueue_active(&pd->wait_q))
                                wake_up_interruptible(&pd->wait_q);
                        return;
                } else if (pd->wakeup) {
                        pd->wakeup(pd->private);
                        if (dev->port->cad) /* racy but no matter */
                                return;
                } else {
                        pr_err("%s: don't know how to wake %s\n",
                               port->name, pd->name);
                }
        }

        /*
         * Nobody was waiting, so walk the list to see if anyone is
         * interested in being woken up. (Note: no locking required)
         */
        /* !!! LOCKING IS NEEDED HERE */
        for (pd = port->devices; !port->cad && pd; pd = pd->next) {
                if (pd->wakeup && pd != dev)
                        pd->wakeup(pd->private);
        }
}
EXPORT_SYMBOL(parport_release);

irqreturn_t parport_irq_handler(int irq, void *dev_id)
{
        struct parport *port = dev_id;

        parport_generic_irq(port);

        return IRQ_HANDLED;
}
EXPORT_SYMBOL(parport_irq_handler);

MODULE_DESCRIPTION("Parallel-port resource manager");
MODULE_LICENSE("GPL");