[alsa-devel] [PATCH 2/8] ALSA: control: obsolete switch statement with const value table

[Lars-Peter Clausen]

On 02/11/2015 11:37 AM, Takashi Sakamoto wrote:
> To check parameters from userspace, snd_ctl_elem_add() has switch
> statement. This statement checks the number of values in a control and
> the size of each value. These two parameters are limited by
> struct snd_ctl_elem_value.value and can be replaced with two sets of two
> dimension array with constant values, without any calculation.
>
> This commit obsolete the switch statement with the array.
>
> Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
> ---
>   sound/core/control.c | 57 +++++++++++++++++++++++++---------------------------
>   1 file changed, 27 insertions(+), 30 deletions(-)
>
> diff --git a/sound/core/control.c b/sound/core/control.c
> index ea49abc..f248bde 100644
> --- a/sound/core/control.c
> +++ b/sound/core/control.c
> @@ -1161,6 +1161,23 @@ static void snd_ctl_elem_user_free(struct snd_kcontrol *kcontrol)
>   static int snd_ctl_elem_add(struct snd_ctl_file *file,
>   			    struct snd_ctl_elem_info *info, int replace)
>   {
> +	/* The capacity of struct snd_ctl_elem_value.value.*/
> +	const unsigned int value_sizes[] = {
> +		[SNDRV_CTL_ELEM_TYPE_BOOLEAN]	= sizeof(long),
> +		[SNDRV_CTL_ELEM_TYPE_INTEGER]	= sizeof(long),
> +		[SNDRV_CTL_ELEM_TYPE_ENUMERATED] = sizeof(unsigned int),
> +		[SNDRV_CTL_ELEM_TYPE_BYTES]	= sizeof(unsigned char),
> +		[SNDRV_CTL_ELEM_TYPE_IEC958]	= sizeof(struct snd_aes_iec958),
> +		[SNDRV_CTL_ELEM_TYPE_INTEGER64] = sizeof(long long),
> +	};
> +	const unsigned int max_value_counts[] = {
> +		[SNDRV_CTL_ELEM_TYPE_BOOLEAN]	= 128,
> +		[SNDRV_CTL_ELEM_TYPE_INTEGER]	= 128,
> +		[SNDRV_CTL_ELEM_TYPE_ENUMERATED] = 128,
> +		[SNDRV_CTL_ELEM_TYPE_BYTES]	= 512,
> +		[SNDRV_CTL_ELEM_TYPE_IEC958]	= 1,
> +		[SNDRV_CTL_ELEM_TYPE_INTEGER64] = 64,
> +	};

The tables should probably be static, no need to put them on the stack.