share.c

来自「linux 内核源代码」· C语言 代码 · 共 1,026 行 · 第 1/2 页

 *	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)(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);
	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);
	}
}

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");