1 files changed, 1014 insertions, 0 deletions

diff --git a/drivers/parport/share.c b/drivers/parport/share.c
new file mode 100644
index 000000000000..ae7becf7efa5
--- /dev/null
+++ b/drivers/parport/share.c
@@ -0,0 +1,1014 @@
+/* $Id: parport_share.c,v 1.15 1998/01/11 12:06:17 philip Exp $
+ * 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/config.h>
+#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 <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 DECLARE_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");
+}
+
+/**
+ *      parport_register_driver - register a parallel port device driver
+ *      @drv: structure describing the driver
+ *
+ *      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.
+ *
+ *      The @drv structure is allocated by the caller and must not be
+ *      deallocated until after calling parport_unregister_driver().
+ *
+ *      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.  Currently it always succeeds.
+ **/
+
+int parport_register_driver (struct parport_driver *drv)
+{
+        struct parport *port;
+
+        if (list_empty(&portlist))
+                get_lowlevel_driver ();
+
+        down(&registration_lock);
+        list_for_each_entry(port, &portlist, list)
+                drv->attach(port);
+        list_add(&drv->list, &drivers);
+        up(&registration_lock);
+
+        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)
+{
+        struct parport *port;
+
+        down(&registration_lock);
+        list_del_init(&drv->list);
+        list_for_each_entry(port, &portlist, list)
+                drv->detach(port);
+        up(&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++) {
+                if (port->probe_info[d].class_name)
+                        kfree (port->probe_info[d].class_name);
+                if (port->probe_info[d].mfr)
+                        kfree (port->probe_info[d].mfr);
+                if (port->probe_info[d].model)
+                        kfree (port->probe_info[d].model);
+                if (port->probe_info[d].cmdset)
+                        kfree (port->probe_info[d].cmdset);
+                if (port->probe_info[d].description)
+                        kfree (port->probe_info[d].description);
+        }
+
+        kfree(port->name);
+        kfree(port);
+}
+
+/**
+ *      parport_get_port - increment a port's reference count
+ *      @port: the port
+ *
+ *      This ensure's that a struct parport pointer remains valid
+ *      until the matching parport_put_port() call.
+ **/
+
+struct parport *parport_get_port (struct parport *port)
+{
+        atomic_inc (&port->ref_count);
+        return 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.
+ **/
+
+void parport_put_port (struct parport *port)
+{
+        if (atomic_dec_and_test (&port->ref_count))
+                /* Can destroy it now. */
+                free_port (port);
+
+        return;
+}
+
+/**
+ *      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;
+        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;
+        init_MUTEX_LOCKED (&tmp->ieee1284.irq); /* actually a semaphore at 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;
+}
+
+/**
+ *      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
+
+        parport_proc_register(port);
+        down(&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);
+        }
+        up(&registration_lock);
+}
+
+/**
+ *      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;
+
+        down(&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);
+
+        up(&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);
+        }
+}
+
+/**
+ *      parport_register_device - register a device on a parallel port
+ *      @port: port to which the device is attached
+ *      @name: a name to refer to the device
+ *      @pf: preemption callback
+ *      @kf: kick callback (wake-up)
+ *      @irq_func: interrupt handler
+ *      @flags: registration flags
+ *      @handle: data for callback functions
+ *
+ *      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 @name is allocated by the caller and must not be
+ *      deallocated until the caller calls @parport_unregister_device
+ *      for that device.
+ *
+ *      The preemption callback function, @pf, is called when this
+ *      device driver has claimed access to the port but another
+ *      device driver wants to use it.  It is given @handle 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, @pf can be %NULL.
+ *
+ *      The wake-up ("kick") callback function, @kf, 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, @kf 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_device(struct parport *port, const char *name,
+                        int (*pf)(void *), void (*kf)(void *),
+                        void (*irq_func)(int, void *, struct pt_regs *), 
+                        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);
+        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;
+}
+
+/**
+ *      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 == NULL) {
+                printk(KERN_ERR "parport_unregister_device: passed NULL\n");
+                return;
+        }
+#endif
+
+        parport_device_proc_unregister(dev);
+
+        port = dev->port->physport;
+
+        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 (&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 (&port->waitlist_lock);
+
+        kfree(dev->state);
+        kfree(dev);
+
+        module_put(port->ops->owner);
+        parport_put_port (port);
+}
+
+/**
+ *      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;
+}
+
+/**
+ *      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;
+}
+
+/**
+ *      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) {
+                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;
+}
+
+/**
+ *      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) {
+                        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;
+}
+
+/**
+ *      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);
+                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);
+        }
+}
+
+/* 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_put_port);
+EXPORT_SYMBOL(parport_find_number);
+EXPORT_SYMBOL(parport_find_base);
+
+MODULE_LICENSE("GPL");