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Linux/sound/core/seq_device.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  *  ALSA sequencer device management
  4  *  Copyright (c) 1999 by Takashi Iwai <tiwai@suse.de>
  5  *
  6  *----------------------------------------------------------------
  7  *
  8  * This device handler separates the card driver module from sequencer
  9  * stuff (sequencer core, synth drivers, etc), so that user can avoid
 10  * to spend unnecessary resources e.g. if he needs only listening to
 11  * MP3s.
 12  *
 13  * The card (or lowlevel) driver creates a sequencer device entry
 14  * via snd_seq_device_new().  This is an entry pointer to communicate
 15  * with the sequencer device "driver", which is involved with the
 16  * actual part to communicate with the sequencer core.
 17  * Each sequencer device entry has an id string and the corresponding
 18  * driver with the same id is loaded when required.  For example,
 19  * lowlevel codes to access emu8000 chip on sbawe card are included in
 20  * emu8000-synth module.  To activate this module, the hardware
 21  * resources like i/o port are passed via snd_seq_device argument.
 22  */
 23 
 24 #include <linux/device.h>
 25 #include <linux/init.h>
 26 #include <linux/module.h>
 27 #include <sound/core.h>
 28 #include <sound/info.h>
 29 #include <sound/seq_device.h>
 30 #include <sound/seq_kernel.h>
 31 #include <sound/initval.h>
 32 #include <linux/kmod.h>
 33 #include <linux/slab.h>
 34 #include <linux/mutex.h>
 35 
 36 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
 37 MODULE_DESCRIPTION("ALSA sequencer device management");
 38 MODULE_LICENSE("GPL");
 39 
 40 /*
 41  * bus definition
 42  */
 43 static int snd_seq_bus_match(struct device *dev, struct device_driver *drv)
 44 {
 45         struct snd_seq_device *sdev = to_seq_dev(dev);
 46         struct snd_seq_driver *sdrv = to_seq_drv(drv);
 47 
 48         return strcmp(sdrv->id, sdev->id) == 0 &&
 49                 sdrv->argsize == sdev->argsize;
 50 }
 51 
 52 static struct bus_type snd_seq_bus_type = {
 53         .name = "snd_seq",
 54         .match = snd_seq_bus_match,
 55 };
 56 
 57 /*
 58  * proc interface -- just for compatibility
 59  */
 60 #ifdef CONFIG_SND_PROC_FS
 61 static struct snd_info_entry *info_entry;
 62 
 63 static int print_dev_info(struct device *dev, void *data)
 64 {
 65         struct snd_seq_device *sdev = to_seq_dev(dev);
 66         struct snd_info_buffer *buffer = data;
 67 
 68         snd_iprintf(buffer, "snd-%s,%s,%d\n", sdev->id,
 69                     dev->driver ? "loaded" : "empty",
 70                     dev->driver ? 1 : 0);
 71         return 0;
 72 }
 73 
 74 static void snd_seq_device_info(struct snd_info_entry *entry,
 75                                 struct snd_info_buffer *buffer)
 76 {
 77         bus_for_each_dev(&snd_seq_bus_type, NULL, buffer, print_dev_info);
 78 }
 79 #endif
 80 
 81 /*
 82  * load all registered drivers (called from seq_clientmgr.c)
 83  */
 84 
 85 #ifdef CONFIG_MODULES
 86 /* flag to block auto-loading */
 87 static atomic_t snd_seq_in_init = ATOMIC_INIT(1); /* blocked as default */
 88 
 89 static int request_seq_drv(struct device *dev, void *data)
 90 {
 91         struct snd_seq_device *sdev = to_seq_dev(dev);
 92 
 93         if (!dev->driver)
 94                 request_module("snd-%s", sdev->id);
 95         return 0;
 96 }
 97 
 98 static void autoload_drivers(struct work_struct *work)
 99 {
100         /* avoid reentrance */
101         if (atomic_inc_return(&snd_seq_in_init) == 1)
102                 bus_for_each_dev(&snd_seq_bus_type, NULL, NULL,
103                                  request_seq_drv);
104         atomic_dec(&snd_seq_in_init);
105 }
106 
107 static DECLARE_WORK(autoload_work, autoload_drivers);
108 
109 static void queue_autoload_drivers(void)
110 {
111         schedule_work(&autoload_work);
112 }
113 
114 void snd_seq_autoload_init(void)
115 {
116         atomic_dec(&snd_seq_in_init);
117 #ifdef CONFIG_SND_SEQUENCER_MODULE
118         /* initial autoload only when snd-seq is a module */
119         queue_autoload_drivers();
120 #endif
121 }
122 EXPORT_SYMBOL(snd_seq_autoload_init);
123 
124 void snd_seq_autoload_exit(void)
125 {
126         atomic_inc(&snd_seq_in_init);
127 }
128 EXPORT_SYMBOL(snd_seq_autoload_exit);
129 
130 void snd_seq_device_load_drivers(void)
131 {
132         queue_autoload_drivers();
133         flush_work(&autoload_work);
134 }
135 EXPORT_SYMBOL(snd_seq_device_load_drivers);
136 #define cancel_autoload_drivers()       cancel_work_sync(&autoload_work)
137 #else
138 #define queue_autoload_drivers() /* NOP */
139 #define cancel_autoload_drivers() /* NOP */
140 #endif
141 
142 /*
143  * device management
144  */
145 static int snd_seq_device_dev_free(struct snd_device *device)
146 {
147         struct snd_seq_device *dev = device->device_data;
148 
149         cancel_autoload_drivers();
150         put_device(&dev->dev);
151         return 0;
152 }
153 
154 static int snd_seq_device_dev_register(struct snd_device *device)
155 {
156         struct snd_seq_device *dev = device->device_data;
157         int err;
158 
159         err = device_add(&dev->dev);
160         if (err < 0)
161                 return err;
162         if (!dev->dev.driver)
163                 queue_autoload_drivers();
164         return 0;
165 }
166 
167 static int snd_seq_device_dev_disconnect(struct snd_device *device)
168 {
169         struct snd_seq_device *dev = device->device_data;
170 
171         device_del(&dev->dev);
172         return 0;
173 }
174 
175 static void snd_seq_dev_release(struct device *dev)
176 {
177         struct snd_seq_device *sdev = to_seq_dev(dev);
178 
179         if (sdev->private_free)
180                 sdev->private_free(sdev);
181         kfree(sdev);
182 }
183 
184 /*
185  * register a sequencer device
186  * card = card info
187  * device = device number (if any)
188  * id = id of driver
189  * result = return pointer (NULL allowed if unnecessary)
190  */
191 int snd_seq_device_new(struct snd_card *card, int device, const char *id,
192                        int argsize, struct snd_seq_device **result)
193 {
194         struct snd_seq_device *dev;
195         int err;
196         static struct snd_device_ops dops = {
197                 .dev_free = snd_seq_device_dev_free,
198                 .dev_register = snd_seq_device_dev_register,
199                 .dev_disconnect = snd_seq_device_dev_disconnect,
200         };
201 
202         if (result)
203                 *result = NULL;
204 
205         if (snd_BUG_ON(!id))
206                 return -EINVAL;
207 
208         dev = kzalloc(sizeof(*dev) + argsize, GFP_KERNEL);
209         if (!dev)
210                 return -ENOMEM;
211 
212         /* set up device info */
213         dev->card = card;
214         dev->device = device;
215         dev->id = id;
216         dev->argsize = argsize;
217 
218         device_initialize(&dev->dev);
219         dev->dev.parent = &card->card_dev;
220         dev->dev.bus = &snd_seq_bus_type;
221         dev->dev.release = snd_seq_dev_release;
222         dev_set_name(&dev->dev, "%s-%d-%d", dev->id, card->number, device);
223 
224         /* add this device to the list */
225         err = snd_device_new(card, SNDRV_DEV_SEQUENCER, dev, &dops);
226         if (err < 0) {
227                 put_device(&dev->dev);
228                 return err;
229         }
230         
231         if (result)
232                 *result = dev;
233 
234         return 0;
235 }
236 EXPORT_SYMBOL(snd_seq_device_new);
237 
238 /*
239  * driver registration
240  */
241 int __snd_seq_driver_register(struct snd_seq_driver *drv, struct module *mod)
242 {
243         if (WARN_ON(!drv->driver.name || !drv->id))
244                 return -EINVAL;
245         drv->driver.bus = &snd_seq_bus_type;
246         drv->driver.owner = mod;
247         return driver_register(&drv->driver);
248 }
249 EXPORT_SYMBOL_GPL(__snd_seq_driver_register);
250 
251 void snd_seq_driver_unregister(struct snd_seq_driver *drv)
252 {
253         driver_unregister(&drv->driver);
254 }
255 EXPORT_SYMBOL_GPL(snd_seq_driver_unregister);
256 
257 /*
258  * module part
259  */
260 
261 static int __init seq_dev_proc_init(void)
262 {
263 #ifdef CONFIG_SND_PROC_FS
264         info_entry = snd_info_create_module_entry(THIS_MODULE, "drivers",
265                                                   snd_seq_root);
266         if (info_entry == NULL)
267                 return -ENOMEM;
268         info_entry->content = SNDRV_INFO_CONTENT_TEXT;
269         info_entry->c.text.read = snd_seq_device_info;
270         if (snd_info_register(info_entry) < 0) {
271                 snd_info_free_entry(info_entry);
272                 return -ENOMEM;
273         }
274 #endif
275         return 0;
276 }
277 
278 static int __init alsa_seq_device_init(void)
279 {
280         int err;
281 
282         err = bus_register(&snd_seq_bus_type);
283         if (err < 0)
284                 return err;
285         err = seq_dev_proc_init();
286         if (err < 0)
287                 bus_unregister(&snd_seq_bus_type);
288         return err;
289 }
290 
291 static void __exit alsa_seq_device_exit(void)
292 {
293 #ifdef CONFIG_MODULES
294         cancel_work_sync(&autoload_work);
295 #endif
296 #ifdef CONFIG_SND_PROC_FS
297         snd_info_free_entry(info_entry);
298 #endif
299         bus_unregister(&snd_seq_bus_type);
300 }
301 
302 subsys_initcall(alsa_seq_device_init)
303 module_exit(alsa_seq_device_exit)
304 

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