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
29 static LIST_HEAD(dongle_list); /* list of registered dongle drivers */
30 static DEFINE_MUTEX(dongle_list_lock); /* protects the list */
31
irda_register_dongle(struct dongle_driver * new)32 int irda_register_dongle(struct dongle_driver *new)
33 {
34 struct list_head *entry;
35 struct dongle_driver *drv;
36
37 IRDA_DEBUG(0, "%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 }
52 EXPORT_SYMBOL(irda_register_dongle);
53
irda_unregister_dongle(struct dongle_driver * drv)54 int 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 }
61 EXPORT_SYMBOL(irda_unregister_dongle);
62
sirdev_get_dongle(struct sir_dev * dev,IRDA_DONGLE type)63 int 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
112 out_reject:
113 dev->dongle_drv = NULL;
114 module_put(drv->owner);
115 out_unlock:
116 mutex_unlock(&dongle_list_lock);
117 return err;
118 }
119
sirdev_put_dongle(struct sir_dev * dev)120 int 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 }
134