linux-kernel - Re: [PATCH RFC v2 3/6] ASoC: soc: qcom: sc8280xp: add support for I2S clocks

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Message-ID: <630bb2b0-0ab4-4083-96a2-9aa485041797@oss.qualcomm.com>
Date: Thu, 9 Oct 2025 11:41:12 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
        Srinivas Kandagatla <srini@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: linux-sound@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH RFC v2 3/6] ASoC: soc: qcom: sc8280xp: add support for I2S
 clocks

On 10/8/25 8:56 PM, Neil Armstrong wrote:
> Add support for getting the I2S clocks used for the MI2S
> interfaces, and enable/disable the clocks on the PCM
> startup and shutdown card callbacks.
> 
> The rate can be easily calculated since the card forces 48Hz,
> 2 channels at 16bit slot size.
> 
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---

[...]

> +static int sc8280xp_snd_i2s_index(struct snd_soc_dai *dai)
> +{
> +	switch (dai->id) {
> +	case PRIMARY_MI2S_RX...PRIMARY_MI2S_TX:

I have mixed feelings about the range syntax here.. it's only 2 entries
per and it's quite error-prone (no errors in this case, but it
encourages the thinking that things are always contiguous)..

[...]

>  	switch (cpu_dai->id) {
>  	case PRIMARY_MI2S_RX...QUATERNARY_MI2S_TX:
>  	case QUINARY_MI2S_RX...QUINARY_MI2S_TX:

whereas e.g. here we see that it's not really the case, but it's
tempting for someone trying to 'clean up' the code to change it to:

case PRIMARY_MI2S_RX...QUINARY_MI2S_TX 

and the reviewers may not catch it

Konrad