linux-kernel - Re: [PATCH v3 1/4] ASoC: qcom: common: Add qcom_snd_tdm_hw

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Date:   Thu, 14 Dec 2023 23:51:50 +0800
From:   Jianhua Lu <lujianhua000@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Banajit Goswami <bgoswami@...cinc.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4] ASoC: qcom: common: Add qcom_snd_tdm_hw_params
 function

On Thu, Dec 14, 2023 at 11:11:06AM +0000, Mark Brown wrote:
> On Wed, Dec 13, 2023 at 08:35:53PM +0800, Jianhua Lu wrote:
> 
> > Add qcom TDM setup function to support TDM ports for qcom platform.
> 
> > +int qcom_snd_tdm_hw_params(struct snd_pcm_substream *substream,
> > +			   struct snd_pcm_hw_params *params)
> > +{
> 
> ...
> 
> > +		ret = snd_soc_dai_set_tdm_slot(cpu_dai, tx_mask, rx_mask, slots, slot_width);
> > +		if (ret < 0) {
> 
> The expectation is that TDM is set up by the machine driver, not from
> hw_params - if the TDM setup can be changed from within hw_params then
> it's hard to see how it's going to interact well with other TDM users on
> the bus.  More usually hw_params() would be influenced by the setup done
> in set_tdm_slot().

Currently, qcom TDM setup need to read hw_params, if we want to move it
to machine driver, we must hardcode some params, but it will reduce reduce
readability.