[alsa-devel] [PATCH 1/2 v4] ALSA: Add snd_ctl_replace() to dynamically replace a control

[Takashi Iwai]

At Wed, 16 Mar 2011 12:16:39 +0000,
Dimitris Papastamos wrote:
> 
> 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 at opensource.wolfsonmicro.com>

Now I applied this one to topic/misc branch with slight coding-style
fixes checkpatch complained.  But I didn't apply the patch for ASoC.

Marc, if you want to take it for ASoC, please pull topic/misc branch
into your tree.


thanks,

Takashi


> ---
>  include/sound/control.h |    1 +
>  sound/core/control.c    |   65 +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 66 insertions(+), 0 deletions(-)
> 
> diff --git a/include/sound/control.h b/include/sound/control.h
> index e67db28..1c8b3ee 100644
> --- a/include/sound/control.h
> +++ b/include/sound/control.h
> @@ -113,6 +113,7 @@ struct snd_kcontrol *snd_ctl_new1(const struct snd_kcontrol_new * kcontrolnew, v
>  void snd_ctl_free_one(struct snd_kcontrol * kcontrol);
>  int snd_ctl_add(struct snd_card * card, struct snd_kcontrol * kcontrol);
>  int snd_ctl_remove(struct snd_card * card, struct snd_kcontrol * kcontrol);
> +int snd_ctl_replace(struct snd_card * card, struct snd_kcontrol * kcontrol, bool add_on_replace);
>  int snd_ctl_remove_id(struct snd_card * card, struct snd_ctl_elem_id *id);
>  int snd_ctl_rename_id(struct snd_card * card, struct snd_ctl_elem_id *src_id, struct snd_ctl_elem_id *dst_id);
>  int snd_ctl_activate_id(struct snd_card *card, struct snd_ctl_elem_id *id,
> diff --git a/sound/core/control.c b/sound/core/control.c
> index db51e4e..a8cae8a 100644
> --- a/sound/core/control.c
> +++ b/sound/core/control.c
> @@ -368,6 +368,71 @@ int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)
>  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
> -- 
> 1.7.4.1
>