[alsa-devel] [PATCH 1/2] ALSA: Add snd_ctl_update() to dynamically update a control

[Takashi Iwai]

At Tue, 15 Mar 2011 12:21:41 +0000,
Dimitris Papastamos wrote:
> 
> Add a function to dynamically update 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 update existing controls.
> A separate patch needs to be made to make ALSA Mixer cope with this.
> 
> Signed-off-by: Dimitris Papastamos <dp at opensource.wolfsonmicro.com>

The change looks OK to me, but I think the name snd_ctl_update() is
a bit confusing.  It sounds as if it updates its content or such.

I thought of snd_ctl_replace(), but this should take two instances or
so ("replace A with B").  If no better name comes up, I'm fine with
snd_ctl_update().


thanks,

Takashi

> ---
>  include/sound/control.h |    1 +
>  sound/core/control.c    |   44 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 45 insertions(+), 0 deletions(-)
> 
> diff --git a/include/sound/control.h b/include/sound/control.h
> index e67db28..12e4de7 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_update(struct snd_card * card, struct snd_kcontrol * kcontrol, int add_on_update);
>  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..db23745 100644
> --- a/sound/core/control.c
> +++ b/sound/core/control.c
> @@ -397,6 +397,50 @@ int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)
>  EXPORT_SYMBOL(snd_ctl_remove);
>  
>  /**
> + * snd_ctl_update - update the control instance of the card
> + * @card: the card instance
> + * @kcontrol: the control instance to update
> + * @add_on_update: add the control if not already added
> + *
> + * Updates the control instance created via snd_ctl_new() or
> + * snd_ctl_new1() of the given card.
> + *
> + * Returns zero if successful, or a negative error code on failure.
> + *
> + */
> +int snd_ctl_update(struct snd_card *card, struct snd_kcontrol *kcontrol,
> +		   int add_on_update)
> +{
> +	struct snd_ctl_elem_id id;
> +	struct snd_kcontrol *old;
> +	int ret;
> +
> +	if (!kcontrol)
> +		return -EINVAL;
> +	if (snd_BUG_ON(!card || !kcontrol->info))
> +		return -EINVAL;
> +	id = kcontrol->id;
> +	down_write(&card->controls_rwsem);
> +	old = snd_ctl_find_id(card, &id);
> +	if (!old) {
> +		up_write(&card->controls_rwsem);
> +		if (add_on_update)
> +			return snd_ctl_add(card, kcontrol);
> +		return -EINVAL;
> +	}
> +	ret = snd_ctl_remove(card, old);
> +	if (ret < 0)
> +		return ret;
> +	up_write(&card->controls_rwsem);
> +	ret = snd_ctl_add(card, kcontrol);
> +	if (ret < 0)
> +		return ret;
> +	return 0;
> +}
> +
> +EXPORT_SYMBOL(snd_ctl_update);
> +
> +/**
>   * snd_ctl_remove_id - remove the control of the given id and release it
>   * @card: the card instance
>   * @id: the control id to remove
> -- 
> 1.7.4.1
>