[ALSA] dynamic minors (3/6): store device-specific object pointers dynamically

Instead of storing the pointers to the device-specific structures in an
array, put them into the struct snd_minor, and look them up dynamically.

This makes the device type modules independent of the minor number
encoding.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

1 files changed, 40 insertions, 6 deletions

diff --git a/sound/core/sound.c b/sound/core/sound.c
index a509f49fa0b4..1e5eca546925 100644
--- a/sound/core/sound.c
+++ b/sound/core/sound.c
@@ -60,7 +60,6 @@ MODULE_ALIAS_CHARDEV_MAJOR(CONFIG_SND_MAJOR);
 int snd_ecards_limit;
 
 static struct snd_minor *snd_minors[SNDRV_OS_MINORS];
-
 static DECLARE_MUTEX(sound_mutex);
 
 extern struct class *sound_class;
@@ -107,6 +106,31 @@ static void snd_request_other(int minor)
 
 #endif                          /* request_module support */
 
+/**
+ * snd_lookup_minor_data - get user data of a registered device
+ * @minor: the minor number
+ * @type: device type (SNDRV_DEVICE_TYPE_XXX)
+ *
+ * Checks that a minor device with the specified type is registered, and returns
+ * its user data pointer.
+ */
+void *snd_lookup_minor_data(unsigned int minor, int type)
+{
+        struct snd_minor *mreg;
+        void *private_data;
+
+        if (minor > ARRAY_SIZE(snd_minors))
+                return NULL;
+        down(&sound_mutex);
+        mreg = snd_minors[minor];
+        if (mreg && mreg->type == type)
+                private_data = mreg->private_data;
+        else
+                private_data = NULL;
+        up(&sound_mutex);
+        return private_data;
+}
+
 static int snd_open(struct inode *inode, struct file *file)
 {
         int minor = iminor(inode);
@@ -183,6 +207,7 @@ static int snd_kernel_minor(int type, struct snd_card *card, int dev)
  * @card: the card instance
  * @dev: the device index
  * @f_ops: the file operations
+ * @private_data: user pointer for f_ops->open()
  * @name: the device file name
  *
  * Registers an ALSA device file for the given card.
@@ -191,7 +216,8 @@ static int snd_kernel_minor(int type, struct snd_card *card, int dev)
  * Retrurns zero if successful, or a negative error code on failure.
  */
 int snd_register_device(int type, struct snd_card *card, int dev,
-                        struct file_operations *f_ops, const char *name)
+                        struct file_operations *f_ops, void *private_data,
+                        const char *name)
 {
         int minor = snd_kernel_minor(type, card, dev);
         struct snd_minor *preg;
@@ -207,6 +233,7 @@ int snd_register_device(int type, struct snd_card *card, int dev,
         preg->card = card ? card->number : -1;
         preg->device = dev;
         preg->f_ops = f_ops;
+        preg->private_data = private_data;
         strcpy(preg->name, name);
         down(&sound_mutex);
         if (snd_minors[minor]) {
@@ -238,13 +265,18 @@ int snd_register_device(int type, struct snd_card *card, int dev,
  */
 int snd_unregister_device(int type, struct snd_card *card, int dev)
 {
-        int minor = snd_kernel_minor(type, card, dev);
+        int cardnum, minor;
         struct snd_minor *mptr;
 
-        if (minor < 0)
-                return minor;
+        cardnum = card ? card->number : -1;
         down(&sound_mutex);
-        if ((mptr = snd_minors[minor]) == NULL) {
+        for (minor = 0; minor < ARRAY_SIZE(snd_minors); ++minor)
+                if ((mptr = snd_minors[minor]) != NULL &&
+                    mptr->type == type &&
+                    mptr->card == cardnum &&
+                    mptr->device == dev)
+                        break;
+        if (minor == ARRAY_SIZE(snd_minors)) {
                 up(&sound_mutex);
                 return -EINVAL;
         }
@@ -392,9 +424,11 @@ EXPORT_SYMBOL(snd_request_card);
 #endif
 EXPORT_SYMBOL(snd_register_device);
 EXPORT_SYMBOL(snd_unregister_device);
+EXPORT_SYMBOL(snd_lookup_minor_data);
 #if defined(CONFIG_SND_OSSEMUL)
 EXPORT_SYMBOL(snd_register_oss_device);
 EXPORT_SYMBOL(snd_unregister_oss_device);
+EXPORT_SYMBOL(snd_lookup_oss_minor_data);
 #endif
   /* memory.c */
 EXPORT_SYMBOL(copy_to_user_fromio);