[alsa-devel] [RFC 2/4] Alsa: control: increment index field for duplicated control.

[Arnaud Pouliquen]

Instead of returning an error when a control is already present, the
index field is incremented and a warning message is printed.
This allows drivers to instanciate same control without
device and sub device number management ( MIXER type controls).

Change-Id: Ifcc60dca9d1cf4c3a424bb9653296678aa7953cb
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen at st.com>
---
 sound/core/control.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/sound/core/control.c b/sound/core/control.c
index fb096cb..014e3f4 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -365,6 +365,7 @@ int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)
 	struct snd_ctl_elem_id id;
 	unsigned int idx;
 	unsigned int count;
+	struct snd_kcontrol *elem_set;
 	int err = -EINVAL;
 
 	if (! kcontrol)
@@ -376,17 +377,24 @@ int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)
 		goto error;
 
 	down_write(&card->controls_rwsem);
-	if (snd_ctl_find_id(card, &id)) {
-		up_write(&card->controls_rwsem);
-		dev_err(card->dev, "control %i:%i:%i:%s:%i is already present\n",
-					id.iface,
-					id.device,
-					id.subdevice,
-					id.name,
-					id.index);
-		err = -EBUSY;
-		goto error;
+	while (elem_set = snd_ctl_find_id(card, &id)) {
+		id.index++;
+		if (id.index > UINT_MAX - kcontrol->count) {
+			up_write(&card->controls_rwsem);
+			dev_err(card->dev, "no more free index for control %i:%i:%i:%s\n",
+				id.iface, id.device, id.subdevice, id.name);
+			err = -ENOSPC;
+			goto error;
+		}
+	}
+	if (kcontrol->id.index != id.index) {
+		dev_warn(card->dev, "control %i:%i:%i:%s:%i is already present\n",
+			 id.iface, id.device, id.subdevice, id.name, id.index);
+		dev_warn(card->dev, "control index updated from %i to %i\n",
+			 kcontrol->id.index, id.index);
+		kcontrol->id.index = id.index;
 	}
+
 	if (snd_ctl_find_hole(card, kcontrol->count) < 0) {
 		up_write(&card->controls_rwsem);
 		err = -ENOMEM;
-- 
1.9.1