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-rw-r--r--Documentation/sound/alsa/ALSA-Configuration.txt21
-rw-r--r--sound/core/init.c36
2 files changed, 56 insertions, 1 deletions
diff --git a/Documentation/sound/alsa/ALSA-Configuration.txt b/Documentation/sound/alsa/ALSA-Configuration.txt
index 8e49c19f6c9..f34821d6d52 100644
--- a/Documentation/sound/alsa/ALSA-Configuration.txt
+++ b/Documentation/sound/alsa/ALSA-Configuration.txt
@@ -57,7 +57,9 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
- Default: 1
- For auto-loading more than one card, specify this
option together with snd-card-X aliases.
-
+ slots - Reserve the slot index for the given driver.
+ This option takes multiple strings.
+ See "Module Autoloading Support" section for details.
Module snd-pcm-oss
------------------
@@ -2140,6 +2142,23 @@ alias sound-slot-1 snd-ens1371
In this example, the interwave card is always loaded as the first card
(index 0) and ens1371 as the second (index 1).
+Alternative (and new) way to fixate the slot assignment is to use
+"slots" option of snd module. In the case above, specify like the
+following:
+
+options snd slots=snd-interwave,snd-ens1371
+
+Then, the first slot (#0) is reserved for snd-interwave driver, and
+the second (#1) for snd-ens1371. You can omit index option in each
+driver if slots option is used (although you can still have them at
+the same time as long as they don't conflict).
+
+The slots option is especially useful for avoiding the possible
+hot-plugging and the resultant slot conflict. For example, in the
+case above again, the first two slots are already reserved. If any
+other driver (e.g. snd-usb-audio) is loaded before snd-interwave or
+snd-ens1371, it will be assigned to the third or later slot.
+
ALSA PCM devices to OSS devices mapping
=======================================
diff --git a/sound/core/init.c b/sound/core/init.c
index 2cb7099eb1e..48d38a79cbb 100644
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -43,6 +43,40 @@ EXPORT_SYMBOL(snd_cards);
static DEFINE_MUTEX(snd_card_mutex);
+static char *slots[SNDRV_CARDS];
+module_param_array(slots, charp, NULL, 0444);
+MODULE_PARM_DESC(slots, "Module names assigned to the slots.");
+
+/* return non-zero if the given index is already reserved for another
+ * module via slots option
+ */
+static int module_slot_mismatch(struct module *module, int idx)
+{
+#ifdef MODULE
+ char *s1, *s2;
+ if (!module || !module->name || !slots[idx])
+ return 0;
+ s1 = slots[idx];
+ s2 = module->name;
+ /* compare module name strings
+ * hyphens are handled as equivalent with underscore
+ */
+ for (;;) {
+ char c1 = *s1++;
+ char c2 = *s2++;
+ if (c1 == '-')
+ c1 = '_';
+ if (c2 == '-')
+ c2 = '_';
+ if (c1 != c2)
+ return 1;
+ if (!c1)
+ break;
+ }
+#endif
+ return 0;
+}
+
#if defined(CONFIG_SND_MIXER_OSS) || defined(CONFIG_SND_MIXER_OSS_MODULE)
int (*snd_mixer_oss_notify_callback)(struct snd_card *card, int free_flag);
EXPORT_SYMBOL(snd_mixer_oss_notify_callback);
@@ -115,6 +149,8 @@ struct snd_card *snd_card_new(int idx, const char *xid,
for (idx2 = 0; idx2 < SNDRV_CARDS; idx2++)
/* idx == -1 == 0xffff means: take any free slot */
if (~snd_cards_lock & idx & 1<<idx2) {
+ if (module_slot_mismatch(module, idx2))
+ continue;
idx = idx2;
if (idx >= snd_ecards_limit)
snd_ecards_limit = idx + 1;