[ALSA] dynamic minors (4/6): dynamic minor number allocation

Modules: ALSA Core,ALSA Minor Numbers

Add an option to allocate device file minor numbers dynamically.

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

3 files changed, 82 insertions, 23 deletions

diff --git a/include/sound/minors.h b/include/sound/minors.h
index a17b5c9961bb..46bcd2023ed8 100644
--- a/include/sound/minors.h
+++ b/include/sound/minors.h
@@ -26,18 +26,20 @@
 #define SNDRV_MINOR_DEVICE(minor)       ((minor) & 0x001f)
 #define SNDRV_MINOR(card, dev)          (((card) << 5) | (dev))
 
-#define SNDRV_MINOR_CONTROL             0       /* 0 - 0 */
+/* these minors can still be used for autoloading devices (/dev/aload*) */
+#define SNDRV_MINOR_CONTROL             0       /* 0 */
 #define SNDRV_MINOR_GLOBAL              1       /* 1 */
 #define SNDRV_MINOR_SEQUENCER           (SNDRV_MINOR_GLOBAL + 0 * 32)
 #define SNDRV_MINOR_TIMER               (SNDRV_MINOR_GLOBAL + 1 * 32)
+
+#ifndef CONFIG_SND_DYNAMIC_MINORS
+                                                /* 2 - 3 (reserved) */
 #define SNDRV_MINOR_HWDEP               4       /* 4 - 7 */
-#define SNDRV_MINOR_HWDEPS              4
 #define SNDRV_MINOR_RAWMIDI             8       /* 8 - 15 */
-#define SNDRV_MINOR_RAWMIDIS            8
 #define SNDRV_MINOR_PCM_PLAYBACK        16      /* 16 - 23 */
 #define SNDRV_MINOR_PCM_CAPTURE         24      /* 24 - 31 */
-#define SNDRV_MINOR_PCMS                8
 
+/* same as first respective minor number to make minor allocation easier */
 #define SNDRV_DEVICE_TYPE_CONTROL       SNDRV_MINOR_CONTROL
 #define SNDRV_DEVICE_TYPE_HWDEP         SNDRV_MINOR_HWDEP
 #define SNDRV_DEVICE_TYPE_RAWMIDI       SNDRV_MINOR_RAWMIDI
@@ -46,6 +48,25 @@
 #define SNDRV_DEVICE_TYPE_SEQUENCER     SNDRV_MINOR_SEQUENCER
 #define SNDRV_DEVICE_TYPE_TIMER         SNDRV_MINOR_TIMER
 
+#else /* CONFIG_SND_DYNAMIC_MINORS */
+
+enum {
+        SNDRV_DEVICE_TYPE_CONTROL,
+        SNDRV_DEVICE_TYPE_SEQUENCER,
+        SNDRV_DEVICE_TYPE_TIMER,
+        SNDRV_DEVICE_TYPE_HWDEP,
+        SNDRV_DEVICE_TYPE_RAWMIDI,
+        SNDRV_DEVICE_TYPE_PCM_PLAYBACK,
+        SNDRV_DEVICE_TYPE_PCM_CAPTURE,
+};
+
+#endif /* CONFIG_SND_DYNAMIC_MINORS */
+
+#define SNDRV_MINOR_HWDEPS              4
+#define SNDRV_MINOR_RAWMIDIS            8
+#define SNDRV_MINOR_PCMS                8
+
+
 #ifdef CONFIG_SND_OSSEMUL
 
 #define SNDRV_MINOR_OSS_DEVICES         16
diff --git a/sound/core/Kconfig b/sound/core/Kconfig
index b46efff2e4c4..83cbe20c9c9e 100644
--- a/sound/core/Kconfig
+++ b/sound/core/Kconfig
@@ -111,6 +111,17 @@ config SND_SEQ_RTCTIMER_DEFAULT
 
           If in doubt, say Y.
 
+config SND_DYNAMIC_MINORS
+        bool "Dynamic device file minor numbers (EXPERIMENTAL)"
+        depends on SND && EXPERIMENTAL
+        help
+          If you say Y here, the minor numbers of ALSA device files in
+          /dev/snd/ are allocated dynamically.  This allows you to have
+          more than 8 sound cards, but requires a dynamic device file
+          system like udev.
+
+          If you are unsure about this, say N here.
+
 config SND_VERBOSE_PRINTK
         bool "Verbose printk"
         depends on SND
diff --git a/sound/core/sound.c b/sound/core/sound.c
index 1e5eca546925..5e22283078fc 100644
--- a/sound/core/sound.c
+++ b/sound/core/sound.c
@@ -133,29 +133,34 @@ void *snd_lookup_minor_data(unsigned int minor, int type)
 
 static int snd_open(struct inode *inode, struct file *file)
 {
-        int minor = iminor(inode);
-        int card = SNDRV_MINOR_CARD(minor);
-        int dev = SNDRV_MINOR_DEVICE(minor);
+        unsigned int minor = iminor(inode);
         struct snd_minor *mptr = NULL;
         struct file_operations *old_fops;
         int err = 0;
 
-        if (dev != SNDRV_MINOR_GLOBAL) {
-                if (snd_cards[card] == NULL) {
+        if (minor > ARRAY_SIZE(snd_minors))
+                return -ENODEV;
+        mptr = snd_minors[minor];
+        if (mptr == NULL) {
 #ifdef CONFIG_KMOD
-                        snd_request_card(card);
+                int dev = SNDRV_MINOR_DEVICE(minor);
+                if (dev == SNDRV_MINOR_CONTROL) {
+                        /* /dev/aloadC? */
+                        int card = SNDRV_MINOR_CARD(minor);
                         if (snd_cards[card] == NULL)
-#endif
-                                return -ENODEV;
-                }
-        } else {
-#ifdef CONFIG_KMOD
-                if ((mptr = snd_minors[minor]) == NULL)
+                                snd_request_card(card);
+                } else if (dev == SNDRV_MINOR_GLOBAL) {
+                        /* /dev/aloadSEQ */
                         snd_request_other(minor);
+                }
+#ifndef CONFIG_SND_DYNAMIC_MINORS
+                /* /dev/snd/{controlC?,seq} */
+                mptr = snd_minors[minor];
+                if (mptr == NULL)
+#endif
 #endif
+                        return -ENODEV;
         }
-        if (mptr == NULL && (mptr = snd_minors[minor]) == NULL)
-                return -ENODEV;
         old_fops = file->f_op;
         file->f_op = fops_get(mptr->f_ops);
         if (file->f_op->open)
@@ -174,6 +179,22 @@ static struct file_operations snd_fops =
         .open =         snd_open
 };
 
+#ifdef CONFIG_SND_DYNAMIC_MINORS
+static int snd_find_free_minor(void)
+{
+        int minor;
+
+        for (minor = 0; minor < ARRAY_SIZE(snd_minors); ++minor) {
+                /* skip minors still used statically for autoloading devices */
+                if (SNDRV_MINOR_DEVICE(minor) == SNDRV_MINOR_CONTROL ||
+                    minor == SNDRV_MINOR_SEQUENCER)
+                        continue;
+                if (!snd_minors[minor])
+                        return minor;
+        }
+        return -EBUSY;
+}
+#else
 static int snd_kernel_minor(int type, struct snd_card *card, int dev)
 {
         int minor;
@@ -200,6 +221,7 @@ static int snd_kernel_minor(int type, struct snd_card *card, int dev)
         snd_assert(minor >= 0 && minor < SNDRV_OS_MINORS, return -EINVAL);
         return minor;
 }
+#endif
 
 /**
  * snd_register_device - Register the ALSA device file for the card
@@ -219,12 +241,10 @@ int snd_register_device(int type, struct snd_card *card, int dev,
                         struct file_operations *f_ops, void *private_data,
                         const char *name)
 {
-        int minor = snd_kernel_minor(type, card, dev);
+        int minor;
         struct snd_minor *preg;
         struct device *device = NULL;
 
-        if (minor < 0)
-                return minor;
         snd_assert(name, return -EINVAL);
         preg = kmalloc(sizeof(struct snd_minor) + strlen(name) + 1, GFP_KERNEL);
         if (preg == NULL)
@@ -236,10 +256,17 @@ int snd_register_device(int type, struct snd_card *card, int dev,
         preg->private_data = private_data;
         strcpy(preg->name, name);
         down(&sound_mutex);
-        if (snd_minors[minor]) {
+#ifdef CONFIG_SND_DYNAMIC_MINORS
+        minor = snd_find_free_minor();
+#else
+        minor = snd_kernel_minor(type, card, dev);
+        if (minor >= 0 && snd_minors[minor])
+                minor = -EBUSY;
+#endif
+        if (minor < 0) {
                 up(&sound_mutex);
                 kfree(preg);
-                return -EBUSY;
+                return minor;
         }
         snd_minors[minor] = preg;
         if (type != SNDRV_DEVICE_TYPE_CONTROL || preg->card >= cards_limit)