Re: [PATCH] ASoC: fsl_asrc: add protection for the asrc of older version

[Nicolin Chen <nicoleotsuka@gmail.com>]

Hi Shengjiu,

On Fri, Mar 01, 2019 at 02:32:38AM +0000, S.j. Wang wrote:
> There is a constraint for the channel number setting on the
> asrc of older version (e.g. imx35), the channel number should
> be even, odd number isn't valid.
> 
> So add protection when the asrc of older version is used.
> 
> Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
> ---
>  sound/soc/fsl/fsl_asrc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/soc/fsl/fsl_asrc.c b/sound/soc/fsl/fsl_asrc.c
> index 528e8b108422..b3b3c5e15ef1 100644
> --- a/sound/soc/fsl/fsl_asrc.c
> +++ b/sound/soc/fsl/fsl_asrc.c
> @@ -109,7 +109,8 @@ static int fsl_asrc_request_pair(int channels, struct fsl_asrc_pair *pair)
>  	if (index == ASRC_INVALID_PAIR) {
>  		dev_err(dev, "all pairs are busy now\n");
>  		ret = -EBUSY;
> -	} else if (asrc_priv->channel_avail < channels) {
> +	} else if (asrc_priv->channel_avail < channels ||
> +		(asrc_priv->channel_bits < 4 && channels % 2 != 0)) {
>  		dev_err(dev, "can't afford required channels: %d\n", channels);

I feel it'd be better to have another else-if, since the existing
error message is against something else.

+	} else if (asrc_priv->channel_bits < 4 && channels & 1) {
+		/* old version of ASRC has channel_bits = 3 */
+  		dev_err(dev, "does not support odd channel number\n");
+  		ret = -EINVAL;

Alternatively, I feel instead of error-out at here, should we add
a HW constraint or at least fence it off at the beginning of the
hw_params()? This is actually nothing specific to the pair-request
function but a hardware constraint.