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Linux/sound/core/sound.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  *  Advanced Linux Sound Architecture
  4  *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
  5  */
  6 
  7 #include <linux/init.h>
  8 #include <linux/slab.h>
  9 #include <linux/time.h>
 10 #include <linux/device.h>
 11 #include <linux/module.h>
 12 #include <sound/core.h>
 13 #include <sound/minors.h>
 14 #include <sound/info.h>
 15 #include <sound/control.h>
 16 #include <sound/initval.h>
 17 #include <linux/kmod.h>
 18 #include <linux/mutex.h>
 19 
 20 static int major = CONFIG_SND_MAJOR;
 21 int snd_major;
 22 EXPORT_SYMBOL(snd_major);
 23 
 24 static int cards_limit = 1;
 25 
 26 MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>");
 27 MODULE_DESCRIPTION("Advanced Linux Sound Architecture driver for soundcards.");
 28 MODULE_LICENSE("GPL");
 29 module_param(major, int, 0444);
 30 MODULE_PARM_DESC(major, "Major # for sound driver.");
 31 module_param(cards_limit, int, 0444);
 32 MODULE_PARM_DESC(cards_limit, "Count of auto-loadable soundcards.");
 33 MODULE_ALIAS_CHARDEV_MAJOR(CONFIG_SND_MAJOR);
 34 
 35 /* this one holds the actual max. card number currently available.
 36  * as default, it's identical with cards_limit option.  when more
 37  * modules are loaded manually, this limit number increases, too.
 38  */
 39 int snd_ecards_limit;
 40 EXPORT_SYMBOL(snd_ecards_limit);
 41 
 42 static struct snd_minor *snd_minors[SNDRV_OS_MINORS];
 43 static DEFINE_MUTEX(sound_mutex);
 44 
 45 #ifdef CONFIG_MODULES
 46 
 47 /**
 48  * snd_request_card - try to load the card module
 49  * @card: the card number
 50  *
 51  * Tries to load the module "snd-card-X" for the given card number
 52  * via request_module.  Returns immediately if already loaded.
 53  */
 54 void snd_request_card(int card)
 55 {
 56         if (snd_card_locked(card))
 57                 return;
 58         if (card < 0 || card >= cards_limit)
 59                 return;
 60         request_module("snd-card-%i", card);
 61 }
 62 EXPORT_SYMBOL(snd_request_card);
 63 
 64 static void snd_request_other(int minor)
 65 {
 66         char *str;
 67 
 68         switch (minor) {
 69         case SNDRV_MINOR_SEQUENCER:     str = "snd-seq";        break;
 70         case SNDRV_MINOR_TIMER:         str = "snd-timer";      break;
 71         default:                        return;
 72         }
 73         request_module(str);
 74 }
 75 
 76 #endif  /* modular kernel */
 77 
 78 /**
 79  * snd_lookup_minor_data - get user data of a registered device
 80  * @minor: the minor number
 81  * @type: device type (SNDRV_DEVICE_TYPE_XXX)
 82  *
 83  * Checks that a minor device with the specified type is registered, and returns
 84  * its user data pointer.
 85  *
 86  * This function increments the reference counter of the card instance
 87  * if an associated instance with the given minor number and type is found.
 88  * The caller must call snd_card_unref() appropriately later.
 89  *
 90  * Return: The user data pointer if the specified device is found. %NULL
 91  * otherwise.
 92  */
 93 void *snd_lookup_minor_data(unsigned int minor, int type)
 94 {
 95         struct snd_minor *mreg;
 96         void *private_data;
 97 
 98         if (minor >= ARRAY_SIZE(snd_minors))
 99                 return NULL;
100         mutex_lock(&sound_mutex);
101         mreg = snd_minors[minor];
102         if (mreg && mreg->type == type) {
103                 private_data = mreg->private_data;
104                 if (private_data && mreg->card_ptr)
105                         get_device(&mreg->card_ptr->card_dev);
106         } else
107                 private_data = NULL;
108         mutex_unlock(&sound_mutex);
109         return private_data;
110 }
111 EXPORT_SYMBOL(snd_lookup_minor_data);
112 
113 #ifdef CONFIG_MODULES
114 static struct snd_minor *autoload_device(unsigned int minor)
115 {
116         int dev;
117         mutex_unlock(&sound_mutex); /* release lock temporarily */
118         dev = SNDRV_MINOR_DEVICE(minor);
119         if (dev == SNDRV_MINOR_CONTROL) {
120                 /* /dev/aloadC? */
121                 int card = SNDRV_MINOR_CARD(minor);
122                 struct snd_card *ref = snd_card_ref(card);
123                 if (!ref)
124                         snd_request_card(card);
125                 else
126                         snd_card_unref(ref);
127         } else if (dev == SNDRV_MINOR_GLOBAL) {
128                 /* /dev/aloadSEQ */
129                 snd_request_other(minor);
130         }
131         mutex_lock(&sound_mutex); /* reacuire lock */
132         return snd_minors[minor];
133 }
134 #else /* !CONFIG_MODULES */
135 #define autoload_device(minor)  NULL
136 #endif /* CONFIG_MODULES */
137 
138 static int snd_open(struct inode *inode, struct file *file)
139 {
140         unsigned int minor = iminor(inode);
141         struct snd_minor *mptr = NULL;
142         const struct file_operations *new_fops;
143         int err = 0;
144 
145         if (minor >= ARRAY_SIZE(snd_minors))
146                 return -ENODEV;
147         mutex_lock(&sound_mutex);
148         mptr = snd_minors[minor];
149         if (mptr == NULL) {
150                 mptr = autoload_device(minor);
151                 if (!mptr) {
152                         mutex_unlock(&sound_mutex);
153                         return -ENODEV;
154                 }
155         }
156         new_fops = fops_get(mptr->f_ops);
157         mutex_unlock(&sound_mutex);
158         if (!new_fops)
159                 return -ENODEV;
160         replace_fops(file, new_fops);
161 
162         if (file->f_op->open)
163                 err = file->f_op->open(inode, file);
164         return err;
165 }
166 
167 static const struct file_operations snd_fops =
168 {
169         .owner =        THIS_MODULE,
170         .open =         snd_open,
171         .llseek =       noop_llseek,
172 };
173 
174 #ifdef CONFIG_SND_DYNAMIC_MINORS
175 static int snd_find_free_minor(int type, struct snd_card *card, int dev)
176 {
177         int minor;
178 
179         /* static minors for module auto loading */
180         if (type == SNDRV_DEVICE_TYPE_SEQUENCER)
181                 return SNDRV_MINOR_SEQUENCER;
182         if (type == SNDRV_DEVICE_TYPE_TIMER)
183                 return SNDRV_MINOR_TIMER;
184 
185         for (minor = 0; minor < ARRAY_SIZE(snd_minors); ++minor) {
186                 /* skip static minors still used for module auto loading */
187                 if (SNDRV_MINOR_DEVICE(minor) == SNDRV_MINOR_CONTROL)
188                         continue;
189                 if (minor == SNDRV_MINOR_SEQUENCER ||
190                     minor == SNDRV_MINOR_TIMER)
191                         continue;
192                 if (!snd_minors[minor])
193                         return minor;
194         }
195         return -EBUSY;
196 }
197 #else
198 static int snd_find_free_minor(int type, struct snd_card *card, int dev)
199 {
200         int minor;
201 
202         switch (type) {
203         case SNDRV_DEVICE_TYPE_SEQUENCER:
204         case SNDRV_DEVICE_TYPE_TIMER:
205                 minor = type;
206                 break;
207         case SNDRV_DEVICE_TYPE_CONTROL:
208                 if (snd_BUG_ON(!card))
209                         return -EINVAL;
210                 minor = SNDRV_MINOR(card->number, type);
211                 break;
212         case SNDRV_DEVICE_TYPE_HWDEP:
213         case SNDRV_DEVICE_TYPE_RAWMIDI:
214         case SNDRV_DEVICE_TYPE_PCM_PLAYBACK:
215         case SNDRV_DEVICE_TYPE_PCM_CAPTURE:
216         case SNDRV_DEVICE_TYPE_COMPRESS:
217                 if (snd_BUG_ON(!card))
218                         return -EINVAL;
219                 minor = SNDRV_MINOR(card->number, type + dev);
220                 break;
221         default:
222                 return -EINVAL;
223         }
224         if (snd_BUG_ON(minor < 0 || minor >= SNDRV_OS_MINORS))
225                 return -EINVAL;
226         if (snd_minors[minor])
227                 return -EBUSY;
228         return minor;
229 }
230 #endif
231 
232 /**
233  * snd_register_device - Register the ALSA device file for the card
234  * @type: the device type, SNDRV_DEVICE_TYPE_XXX
235  * @card: the card instance
236  * @dev: the device index
237  * @f_ops: the file operations
238  * @private_data: user pointer for f_ops->open()
239  * @device: the device to register
240  *
241  * Registers an ALSA device file for the given card.
242  * The operators have to be set in reg parameter.
243  *
244  * Return: Zero if successful, or a negative error code on failure.
245  */
246 int snd_register_device(int type, struct snd_card *card, int dev,
247                         const struct file_operations *f_ops,
248                         void *private_data, struct device *device)
249 {
250         int minor;
251         int err = 0;
252         struct snd_minor *preg;
253 
254         if (snd_BUG_ON(!device))
255                 return -EINVAL;
256 
257         preg = kmalloc(sizeof *preg, GFP_KERNEL);
258         if (preg == NULL)
259                 return -ENOMEM;
260         preg->type = type;
261         preg->card = card ? card->number : -1;
262         preg->device = dev;
263         preg->f_ops = f_ops;
264         preg->private_data = private_data;
265         preg->card_ptr = card;
266         mutex_lock(&sound_mutex);
267         minor = snd_find_free_minor(type, card, dev);
268         if (minor < 0) {
269                 err = minor;
270                 goto error;
271         }
272 
273         preg->dev = device;
274         device->devt = MKDEV(major, minor);
275         err = device_add(device);
276         if (err < 0)
277                 goto error;
278 
279         snd_minors[minor] = preg;
280  error:
281         mutex_unlock(&sound_mutex);
282         if (err < 0)
283                 kfree(preg);
284         return err;
285 }
286 EXPORT_SYMBOL(snd_register_device);
287 
288 /**
289  * snd_unregister_device - unregister the device on the given card
290  * @dev: the device instance
291  *
292  * Unregisters the device file already registered via
293  * snd_register_device().
294  *
295  * Return: Zero if successful, or a negative error code on failure.
296  */
297 int snd_unregister_device(struct device *dev)
298 {
299         int minor;
300         struct snd_minor *preg;
301 
302         mutex_lock(&sound_mutex);
303         for (minor = 0; minor < ARRAY_SIZE(snd_minors); ++minor) {
304                 preg = snd_minors[minor];
305                 if (preg && preg->dev == dev) {
306                         snd_minors[minor] = NULL;
307                         device_del(dev);
308                         kfree(preg);
309                         break;
310                 }
311         }
312         mutex_unlock(&sound_mutex);
313         if (minor >= ARRAY_SIZE(snd_minors))
314                 return -ENOENT;
315         return 0;
316 }
317 EXPORT_SYMBOL(snd_unregister_device);
318 
319 #ifdef CONFIG_SND_PROC_FS
320 /*
321  *  INFO PART
322  */
323 static const char *snd_device_type_name(int type)
324 {
325         switch (type) {
326         case SNDRV_DEVICE_TYPE_CONTROL:
327                 return "control";
328         case SNDRV_DEVICE_TYPE_HWDEP:
329                 return "hardware dependent";
330         case SNDRV_DEVICE_TYPE_RAWMIDI:
331                 return "raw midi";
332         case SNDRV_DEVICE_TYPE_PCM_PLAYBACK:
333                 return "digital audio playback";
334         case SNDRV_DEVICE_TYPE_PCM_CAPTURE:
335                 return "digital audio capture";
336         case SNDRV_DEVICE_TYPE_SEQUENCER:
337                 return "sequencer";
338         case SNDRV_DEVICE_TYPE_TIMER:
339                 return "timer";
340         default:
341                 return "?";
342         }
343 }
344 
345 static void snd_minor_info_read(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
346 {
347         int minor;
348         struct snd_minor *mptr;
349 
350         mutex_lock(&sound_mutex);
351         for (minor = 0; minor < SNDRV_OS_MINORS; ++minor) {
352                 if (!(mptr = snd_minors[minor]))
353                         continue;
354                 if (mptr->card >= 0) {
355                         if (mptr->device >= 0)
356                                 snd_iprintf(buffer, "%3i: [%2i-%2i]: %s\n",
357                                             minor, mptr->card, mptr->device,
358                                             snd_device_type_name(mptr->type));
359                         else
360                                 snd_iprintf(buffer, "%3i: [%2i]   : %s\n",
361                                             minor, mptr->card,
362                                             snd_device_type_name(mptr->type));
363                 } else
364                         snd_iprintf(buffer, "%3i:        : %s\n", minor,
365                                     snd_device_type_name(mptr->type));
366         }
367         mutex_unlock(&sound_mutex);
368 }
369 
370 int __init snd_minor_info_init(void)
371 {
372         struct snd_info_entry *entry;
373 
374         entry = snd_info_create_module_entry(THIS_MODULE, "devices", NULL);
375         if (!entry)
376                 return -ENOMEM;
377         entry->c.text.read = snd_minor_info_read;
378         return snd_info_register(entry); /* freed in error path */
379 }
380 #endif /* CONFIG_SND_PROC_FS */
381 
382 /*
383  *  INIT PART
384  */
385 
386 static int __init alsa_sound_init(void)
387 {
388         snd_major = major;
389         snd_ecards_limit = cards_limit;
390         if (register_chrdev(major, "alsa", &snd_fops)) {
391                 pr_err("ALSA core: unable to register native major device number %d\n", major);
392                 return -EIO;
393         }
394         if (snd_info_init() < 0) {
395                 unregister_chrdev(major, "alsa");
396                 return -ENOMEM;
397         }
398 #ifndef MODULE
399         pr_info("Advanced Linux Sound Architecture Driver Initialized.\n");
400 #endif
401         return 0;
402 }
403 
404 static void __exit alsa_sound_exit(void)
405 {
406         snd_info_done();
407         unregister_chrdev(major, "alsa");
408 }
409 
410 subsys_initcall(alsa_sound_init);
411 module_exit(alsa_sound_exit);
412 

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