PageRenderTime 24ms CodeModel.GetById 13ms app.highlight 8ms RepoModel.GetById 1ms app.codeStats 0ms

/drivers/net/irda/sir_dongle.c

http://github.com/mirrors/linux
C | 133 lines | 82 code | 24 blank | 27 comment | 12 complexity | 6a8502d0172cc78b18bc5b3682c3adad MD5 | raw file
  1/*********************************************************************
  2 *
  3 *	sir_dongle.c:	manager for serial dongle protocol drivers
  4 *
  5 *	Copyright (c) 2002 Martin Diehl
  6 *
  7 *	This program is free software; you can redistribute it and/or 
  8 *	modify it under the terms of the GNU General Public License as 
  9 *	published by the Free Software Foundation; either version 2 of 
 10 *	the License, or (at your option) any later version.
 11 *
 12 ********************************************************************/    
 13
 14#include <linux/module.h>
 15#include <linux/kernel.h>
 16#include <linux/kmod.h>
 17#include <linux/mutex.h>
 18
 19#include <net/irda/irda.h>
 20
 21#include "sir-dev.h"
 22
 23/**************************************************************************
 24 *
 25 * dongle registration and attachment
 26 *
 27 */
 28
 29static LIST_HEAD(dongle_list);			/* list of registered dongle drivers */
 30static DEFINE_MUTEX(dongle_list_lock);		/* protects the list */
 31
 32int irda_register_dongle(struct dongle_driver *new)
 33{
 34	struct list_head *entry;
 35	struct dongle_driver *drv;
 36
 37	pr_debug("%s : registering dongle \"%s\" (%d).\n",
 38		 __func__, new->driver_name, new->type);
 39
 40	mutex_lock(&dongle_list_lock);
 41	list_for_each(entry, &dongle_list) {
 42		drv = list_entry(entry, struct dongle_driver, dongle_list);
 43		if (new->type == drv->type) {
 44			mutex_unlock(&dongle_list_lock);
 45			return -EEXIST;
 46		}
 47	}
 48	list_add(&new->dongle_list, &dongle_list);
 49	mutex_unlock(&dongle_list_lock);
 50	return 0;
 51}
 52EXPORT_SYMBOL(irda_register_dongle);
 53
 54int irda_unregister_dongle(struct dongle_driver *drv)
 55{
 56	mutex_lock(&dongle_list_lock);
 57	list_del(&drv->dongle_list);
 58	mutex_unlock(&dongle_list_lock);
 59	return 0;
 60}
 61EXPORT_SYMBOL(irda_unregister_dongle);
 62
 63int sirdev_get_dongle(struct sir_dev *dev, IRDA_DONGLE type)
 64{
 65	struct list_head *entry;
 66	const struct dongle_driver *drv = NULL;
 67	int err = -EINVAL;
 68
 69	request_module("irda-dongle-%d", type);
 70
 71	if (dev->dongle_drv != NULL)
 72		return -EBUSY;
 73	
 74	/* serialize access to the list of registered dongles */
 75	mutex_lock(&dongle_list_lock);
 76
 77	list_for_each(entry, &dongle_list) {
 78		drv = list_entry(entry, struct dongle_driver, dongle_list);
 79		if (drv->type == type)
 80			break;
 81		else
 82			drv = NULL;
 83	}
 84
 85	if (!drv) {
 86		err = -ENODEV;
 87		goto out_unlock;	/* no such dongle */
 88	}
 89
 90	/* handling of SMP races with dongle module removal - three cases:
 91	 * 1) dongle driver was already unregistered - then we haven't found the
 92	 *	requested dongle above and are already out here
 93	 * 2) the module is already marked deleted but the driver is still
 94	 *	registered - then the try_module_get() below will fail
 95	 * 3) the try_module_get() below succeeds before the module is marked
 96	 *	deleted - then sys_delete_module() fails and prevents the removal
 97	 *	because the module is in use.
 98	 */
 99
100	if (!try_module_get(drv->owner)) {
101		err = -ESTALE;
102		goto out_unlock;	/* rmmod already pending */
103	}
104	dev->dongle_drv = drv;
105
106	if (!drv->open  ||  (err=drv->open(dev))!=0)
107		goto out_reject;		/* failed to open driver */
108
109	mutex_unlock(&dongle_list_lock);
110	return 0;
111
112out_reject:
113	dev->dongle_drv = NULL;
114	module_put(drv->owner);
115out_unlock:
116	mutex_unlock(&dongle_list_lock);
117	return err;
118}
119
120int sirdev_put_dongle(struct sir_dev *dev)
121{
122	const struct dongle_driver *drv = dev->dongle_drv;
123
124	if (drv) {
125		if (drv->close)
126			drv->close(dev);		/* close this dongle instance */
127
128		dev->dongle_drv = NULL;			/* unlink the dongle driver */
129		module_put(drv->owner);/* decrement driver's module refcount */
130	}
131
132	return 0;
133}