Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

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");