ALSA: Add snd_ctl_replace() to dynamically replace a control
Add a function to dynamically replace a given control. If the
control does not already exist, a third parameter is used to determine
whether to actually add that control. This is useful in cases where
downloadable firmware at runtime can add or replace existing controls.
A separate patch needs to be made to allow ALSA Mixer to render the
replaced controls on the fly.
Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/control.c b/sound/core/control.c
index a08ad57..5d98194 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -366,6 +366,70 @@
EXPORT_SYMBOL(snd_ctl_add);
/**
+ * snd_ctl_replace - replace the control instance of the card
+ * @card: the card instance
+ * @kcontrol: the control instance to replace
+ * @add_on_replace: add the control if not already added
+ *
+ * Replaces the given control. If the given control does not exist
+ * and the add_on_replace flag is set, the control is added. If the
+ * control exists, it is destroyed first.
+ *
+ * Returns zero if successful, or a negative error code on failure.
+ *
+ * It frees automatically the control which cannot be added or replaced.
+ */
+int snd_ctl_replace(struct snd_card *card, struct snd_kcontrol *kcontrol,
+ bool add_on_replace)
+{
+ struct snd_ctl_elem_id id;
+ unsigned int idx;
+ struct snd_kcontrol *old;
+ int ret;
+
+ if (!kcontrol)
+ return -EINVAL;
+ if (snd_BUG_ON(!card || !kcontrol->info)) {
+ ret = -EINVAL;
+ goto error;
+ }
+ id = kcontrol->id;
+ down_write(&card->controls_rwsem);
+ old = snd_ctl_find_id(card, &id);
+ if (!old) {
+ if (add_on_replace)
+ goto add;
+ up_write(&card->controls_rwsem);
+ ret = -EINVAL;
+ goto error;
+ }
+ ret = snd_ctl_remove(card, old);
+ if (ret < 0) {
+ up_write(&card->controls_rwsem);
+ goto error;
+ }
+add:
+ if (snd_ctl_find_hole(card, kcontrol->count) < 0) {
+ up_write(&card->controls_rwsem);
+ ret = -ENOMEM;
+ goto error;
+ }
+ list_add_tail(&kcontrol->list, &card->controls);
+ card->controls_count += kcontrol->count;
+ kcontrol->id.numid = card->last_numid + 1;
+ card->last_numid += kcontrol->count;
+ up_write(&card->controls_rwsem);
+ for (idx = 0; idx < kcontrol->count; idx++, id.index++, id.numid++)
+ snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &id);
+ return 0;
+
+error:
+ snd_ctl_free_one(kcontrol);
+ return ret;
+}
+EXPORT_SYMBOL(snd_ctl_replace);
+
+/**
* snd_ctl_remove - remove the control from the card and release it
* @card: the card instance
* @kcontrol: the control instance to remove