Re: [PATCH v5 1/5] ASoC: ops: improve snd_soc_get_volsw

[Richard Acayan <mailingradian@gmail.com>]

On Fri, Sep 12, 2025 at 02:06:20PM +0530, Niranjan H Y wrote:
> * add error handling in case register read fails
> * clamp the values if the register value read is
>   out of range
> 
> Signed-off-by: Niranjan H Y <niranjan.hy@ti.com>
> --
> v5:
>  - remove clamp parameter
>  - move the boundary check after sign-bit extension
> ---
>  sound/soc/soc-ops.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/soc-ops.c b/sound/soc/soc-ops.c
> index a629e0eac..03f74c32d 100644
> --- a/sound/soc/soc-ops.c
> +++ b/sound/soc/soc-ops.c
> @@ -118,6 +118,7 @@ static int soc_mixer_reg_to_ctl(struct soc_mixer_control *mc, unsigned int reg_v
>  	if (mc->sign_bit)
>  		val = sign_extend32(val, mc->sign_bit);
>  
> +	val = clamp(val, mc->min, mc->max);

This code path is shared with SX controls, when the maximum would be
mc->min + mc->max. The max parameter to the function can be used to get
a more sensible maximum (otherwise there could be cases where min > max):

	mc->min + max

Also, the Digital PCM Volume in CS35L36 has some trouble with this. It
maps -102dB to 0x4D0 and -0.125dB to 0x7FF (mask 0x7FF). At +0dB,
it's supposed to wrap around to 0x000, then go up to +12dB at 0x060.
This clamping reads +0dB and above (0x000 to 0x060) as -102dB, since it
doesn't account for signed values.