share.c

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/*
 * Parallel-port resource manager code.
 * 
 * Authors: David Campbell <[email protected]>
 *          Tim Waugh <[email protected]>
 *          Jose Renau <[email protected]>
 *          Philip Blundell <[email protected]>
 *      Andrea Arcangeli
 *
 * based on work by Grant Guenther <[email protected]>
 *          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.h>
#include <linux/kmod.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 LIST_HEAD(drivers);

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,
};

/* Call attach(port) for each registered driver. */
static void attach_driver_chain(struct parport *port)
{
    /* caller has exclusive registration_lock */
    struct parport_driver *drv;
    list_for_each_entry(drv, &drivers, list)
        drv->attach(port);
}

/* Call detach(port) for each registered driver. */
static void detach_driver_chain(struct parport *port)
{
    struct parport_driver *drv;
    /* caller has exclusive registration_lock */
    list_for_each_entry(drv, &drivers, list)
        drv->detach (port);
}

/* 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");
}

int parport_register_driver (struct parport_driver *drv)
{
    struct parport *port;

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

    mutex_lock(&registration_lock);
    list_for_each_entry(port, &portlist, list)
        drv->attach(port);
    list_add(&drv->list, &drivers);
    mutex_unlock(&registration_lock);

    return 0;
}

void parport_unregister_driver (struct parport_driver *drv)
{
    struct parport *port;

    mutex_lock(&registration_lock);
    list_del_init(&drv->list);
    list_for_each_entry(port, &portlist, list)
        drv->detach(port);
    mutex_unlock(&registration_lock);
}

static void free_port (struct parport *port)
{
    int d;
    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->name);
    kfree(port);
}

struct parport *parport_get_port (struct parport *port)
{
    atomic_inc (&port->ref_count);
    return port;
}

void parport_put_port (struct parport *port)
{
    if (atomic_dec_and_test (&port->ref_count))
        /* Can destroy it now. */
        free_port (port);

    return;
}

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;
    char *name;

    tmp = kmalloc(sizeof(struct parport), GFP_KERNEL);
    if (!tmp) {
        printk(KERN_WARNING "parport: memory squeeze\n");
        return NULL;
    }

    /* Init our structure */
    memset(tmp, 0, sizeof(struct parport));
    tmp->base = base;
    tmp->irq = irq;
    tmp->dma = dma;
    tmp->muxport = tmp->daisy = tmp->muxsel = -1;
    tmp->modes = 0;
    INIT_LIST_HEAD(&tmp->list);
    tmp->devices = tmp->cad = NULL;
    tmp->flags = 0;
    tmp->ops = ops;
    tmp->physport = tmp;
    memset (tmp->probe_info, 0, 5 * sizeof (struct parport_device_info));
    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);
    INIT_LIST_HEAD(&tmp->full_list);

    name = kmalloc(15, GFP_KERNEL);
    if (!name) {
        printk(KERN_ERR "parport: memory squeeze\n");
        kfree(tmp);
        return NULL;
    }
    /* Search for the lowest free parport number. */

    spin_lock(&full_list_lock);
    for (l = all_ports.next, num = 0; l != &all_ports; l = l->next, num++) {
        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.
     */
    sprintf(name, "parport%d", tmp->portnum = tmp->number);
    tmp->name = name;

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

    tmp->waithead = tmp->waittail = NULL;

    return tmp;
}

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)
        printk(KERN_WARNING "%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);
}

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);
    }
}

struct pardevice *
parport_register_device(struct parport *port, const char *name,
            int (*pf)(void *), void (*kf)(void *),
            void (*irq_func)(void *), 
            int flags, void *handle)
{
    struct pardevice *tmp;

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

    if (flags & PARPORT_DEV_LURK) {
        if (!pf || !kf) {
            printk(KERN_INFO "%s: refused to register lurking device (%s) without callbacks\n", port->name, name);
            return NULL;
        }
    }

    /* We up our own module reference count, and that of the port
           on which a device is to be registered, to ensure that
           neither of us gets unloaded while we sleep in (e.g.)
           kmalloc.
         */
    if (!try_module_get(port->ops->owner)) {
        return NULL;
    }
        
    parport_get_port (port);

    tmp = kmalloc(sizeof(struct pardevice), GFP_KERNEL);
    if (tmp == NULL) {
        printk(KERN_WARNING "%s: memory squeeze, couldn't register %s.\n", port->name, name);
        goto out;
    }

    tmp->state = kmalloc(sizeof(struct parport_state), GFP_KERNEL);
    if (tmp->state == NULL) {
        printk(KERN_WARNING "%s: memory squeeze, couldn't register %s.\n", port->name, name);
        goto out_free_pardevice;
    }

    tmp->name = name;
    tmp->port = port;
    tmp->daisy = -1;
    tmp->preempt = pf;
    tmp->wakeup = kf;
    tmp->private = handle;
    tmp->flags = flags;
    tmp->irq_func = irq_func;
    tmp->waiting = 0;
    tmp->timeout = 5 * HZ;

    /* Chain this onto the list */
    tmp->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 (flags & PARPORT_DEV_EXCL) {
        if (port->physport->devices) {
            spin_unlock (&port->physport->pardevice_lock);
            printk (KERN_DEBUG
                "%s: cannot grant exclusive access for "
                "device %s\n", port->name, name);
            goto out_free_all;
        }
        port->flags |= PARPORT_FLAG_EXCL;
    }

    tmp->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 = tmp;
    port->physport->devices = tmp;
    spin_unlock(&port->physport->pardevice_lock);

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

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

 out_free_all:
    kfree(tmp->state);
 out_free_pardevice:
    kfree(tmp);
 out:
    parport_put_port (port);
    module_put(port->ops->owner);

    return NULL;
}

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

#ifdef PARPORT_PARANOID
    if (dev == NULL) {
        printk(KERN_ERR "parport_unregister_device: passed NULL\n");
        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);
    kfree(dev);

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

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;
}

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

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

    /* Preempt any current device */
    write_lock_irqsave (&port->cad_lock, flags);
    if ((oldcad = port->cad) != NULL) {
        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.. */
            printk(KERN_WARNING
                   "%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;
}

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) {
            interruptible_sleep_on (&dev->wait_q);
            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;
}

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);
        printk(KERN_WARNING "%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 {
            printk(KERN_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 == NULL) && pd; pd = pd->next) {
        if (pd->wakeup && pd != dev)
            pd->wakeup(pd->private);
    }
}

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

    parport_generic_irq(port);

    return IRQ_HANDLED;
}

/* Exported symbols for modules. */

EXPORT_SYMBOL(parport_claim);
EXPORT_SYMBOL(parport_claim_or_block);
EXPORT_SYMBOL(parport_release);
EXPORT_SYMBOL(parport_register_port);
EXPORT_SYMBOL(parport_announce_port);
EXPORT_SYMBOL(parport_remove_port);
EXPORT_SYMBOL(parport_register_driver);
EXPORT_SYMBOL(parport_unregister_driver);
EXPORT_SYMBOL(parport_register_device);
EXPORT_SYMBOL(parport_unregister_device);
EXPORT_SYMBOL(parport_get_port);
EXPORT_SYMBOL(parport_put_port);
EXPORT_SYMBOL(parport_find_number);
EXPORT_SYMBOL(parport_find_base);
EXPORT_SYMBOL(parport_irq_handler);

MODULE_LICENSE("GPL");