[PATCH] ALSA: introduce snd_card_make_id_unique()

[Daniel Mack]

Sound card drivers may choose their own way to provide a nice sound card
ID, especially when the default behaviour taken by choose_default_name()
is not appropriate. ALSA's IDs must be unique, so there is need for some
core logic to ensure that.

This patch adds the function snd_card_make_id_unique() to the ALSA core
which lowlevel drivers can call to make sure the computed string isn't
already taken.

Signed-off-by: Daniel Mack <daniel at caiaq.de>
Cc: Takashi Iwai <tiwai at suse.de>
Cc: Jaroslav Kysela <perex at perex.cz>
---
 include/sound/core.h |    1 +
 sound/core/init.c    |   45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/include/sound/core.h b/include/sound/core.h
index 3dea798..01ea816 100644
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -319,6 +319,7 @@ int snd_card_info_done(void);
 int snd_component_add(struct snd_card *card, const char *component);
 int snd_card_file_add(struct snd_card *card, struct file *file);
 int snd_card_file_remove(struct snd_card *card, struct file *file);
+void snd_card_make_id_unique(struct snd_card *card);
 
 #ifndef snd_card_set_dev
 #define snd_card_set_dev(card, devptr) ((card)->dev = (devptr))
diff --git a/sound/core/init.c b/sound/core/init.c
index fd56afe..8503a01 100644
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -547,6 +547,51 @@ static void choose_default_id(struct snd_card *card)
 	}
 }
 
+static int
+card_id_is_ambiguous(struct snd_card *card, const char *id)
+{
+	int i;
+
+	for (i = 0; i < snd_ecards_limit; i++) {
+		/* only run for exisiting cards but not for the
+		 * one in question */
+		if (i == card->number || !snd_cards[i])
+			continue;
+
+		if (strcmp(snd_cards[i]->id, id) == 0)
+			return 1;
+	}
+
+	return 0;
+}
+
+void
+snd_card_make_id_unique(struct snd_card *card)
+{
+	int count = 1;
+	char id[sizeof(card->id)];
+
+	if (*card->id == '\0')
+		return;
+
+	strlcpy(id, card->id, sizeof(id));
+
+	while (card_id_is_ambiguous(card, id)) {
+		/* As we need to add some characters to the id, make
+		 * sure there's enough room for it */
+		int maxlen = sizeof(card->id) - (2 + (count / 10));
+
+		if (strlen(card->id) > maxlen)
+			card->id[maxlen] = '\0';
+
+		snprintf(id, sizeof(id), "%s_%d", card->id, count);
+		count++;
+	}
+
+	strlcpy(card->id, id, sizeof(id));
+}
+EXPORT_SYMBOL_GPL(snd_card_make_id_unique);
+
 #ifndef CONFIG_SYSFS_DEPRECATED
 static ssize_t
 card_id_show_attr(struct device *dev,
-- 
1.6.3.1