[alsa-devel] [PATCH] ALSA: control: Simplify snd_ctl_elem_list() implementation

[Takashi Sakamoto]

Hi,

On May 23 2017 00:52, Takashi Iwai wrote:
> This patch simplifies the code of snd_ctl_elem_list() in the following
> ways:
> 
> - Avoid a vmalloc() temporary buffer but do copy in each iteration;
>    the vmalloc buffer was introduced at the time we took the spinlock
>    for the ctl element management.
> 
> - Use the standard list_for_each_entry() macro
> 
> - Merge two loops into one;
>    it used to be a loop for skipping until offset becomes zero and
>    another loop to copy the data.  They can be folded into a single
>    loop easily.
> 
> Signed-off-by: Takashi Iwai <tiwai at suse.de>

Reviewed-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
Tested-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>

I have one comment.

> ---
>   sound/core/control.c | 66 +++++++++++++++++++---------------------------------
>   1 file changed, 24 insertions(+), 42 deletions(-)
> 
> diff --git a/sound/core/control.c b/sound/core/control.c
> index c109b82eef4b..47080da8451a 100644
> --- a/sound/core/control.c
> +++ b/sound/core/control.c
> @@ -747,11 +747,11 @@ static int snd_ctl_card_info(struct snd_card *card, struct snd_ctl_file * ctl,
>   static int snd_ctl_elem_list(struct snd_card *card,
>   			     struct snd_ctl_elem_list __user *_list)
>   {
> -	struct list_head *plist;
>   	struct snd_ctl_elem_list list;
>   	struct snd_kcontrol *kctl;
> -	struct snd_ctl_elem_id *dst, *id;
> +	struct snd_ctl_elem_id id;
>   	unsigned int offset, space, jidx;
> +	int err = 0;
>   	
>   	if (copy_from_user(&list, _list, sizeof(list)))
>   		return -EFAULT;
> @@ -760,52 +760,34 @@ static int snd_ctl_elem_list(struct snd_card *card,
>   	/* try limit maximum space */
>   	if (space > 16384)
>   		return -ENOMEM;

We can get rid of this limitation because allocation in kernel space is 
not performed anymore.


Regards

Takashi Sakamoto