/********************************************************************* * *	sir_dongle.c:	manager for serial dongle protocol drivers * *	Copyright (c) 2002 Martin Diehl * *	This program is free software; you can redistribute it and/or  *	modify it under the terms of the GNU General Public License as  *	published by the Free Software Foundation; either version 2 of  *	the License, or (at your option) any later version. * ********************************************************************/    #include <linux/module.h>#include <linux/kernel.h>#include <linux/init.h>#include <linux/smp_lock.h>#include <linux/kmod.h>#include <net/irda/irda.h>#include "sir-dev.h"/************************************************************************** * * dongle registration and attachment * */static LIST_HEAD(dongle_list);			/* list of registered dongle drivers */static DECLARE_MUTEX(dongle_list_lock);		/* protects the list */int irda_register_dongle(struct dongle_driver *new){	struct list_head *entry;	struct dongle_driver *drv;	IRDA_DEBUG(0, "%s : registering dongle \"%s\" (%d).\n",		   __FUNCTION__, new->driver_name, new->type);	down(&dongle_list_lock);	list_for_each(entry, &dongle_list) {		drv = list_entry(entry, struct dongle_driver, dongle_list);		if (new->type == drv->type) {			up(&dongle_list_lock);			return -EEXIST;		}	}	list_add(&new->dongle_list, &dongle_list);	up(&dongle_list_lock);	return 0;}int irda_unregister_dongle(struct dongle_driver *drv){	down(&dongle_list_lock);	list_del(&drv->dongle_list);	up(&dongle_list_lock);	return 0;}int sirdev_get_dongle(struct sir_dev *dev, IRDA_DONGLE type){	struct list_head *entry;	const struct dongle_driver *drv = NULL;	int err = -EINVAL;#ifdef CONFIG_KMOD	request_module("irda-dongle-%d", type);#endif	if (dev->dongle_drv != NULL)		return -EBUSY;		/* serialize access to the list of registered dongles */	down(&dongle_list_lock);	list_for_each(entry, &dongle_list) {		drv = list_entry(entry, struct dongle_driver, dongle_list);		if (drv->type == type)			break;		else			drv = NULL;	}	if (!drv) {		err = -ENODEV;		goto out_unlock;	/* no such dongle */	}	/* handling of SMP races with dongle module removal - three cases:	 * 1) dongle driver was already unregistered - then we haven't found the	 *	requested dongle above and are already out here	 * 2) the module is already marked deleted but the driver is still	 *	registered - then the try_module_get() below will fail	 * 3) the try_module_get() below succeeds before the module is marked	 *	deleted - then sys_delete_module() fails and prevents the removal	 *	because the module is in use.	 */	if (!try_module_get(drv->owner)) {		err = -ESTALE;		goto out_unlock;	/* rmmod already pending */	}	dev->dongle_drv = drv;	if (!drv->open  ||  (err=drv->open(dev))!=0)		goto out_reject;		/* failed to open driver */	up(&dongle_list_lock);	return 0;out_reject:	dev->dongle_drv = NULL;	module_put(drv->owner);out_unlock:	up(&dongle_list_lock);	return err;}int sirdev_put_dongle(struct sir_dev *dev){	const struct dongle_driver *drv = dev->dongle_drv;	if (drv) {		if (drv->close)			drv->close(dev);		/* close this dongle instance */		dev->dongle_drv = NULL;			/* unlink the dongle driver */		module_put(drv->owner);/* decrement driver's module refcount */	}	return 0;}