linux-kernel - Re: [PATCH 1/3] ASoC: mediatek: mt8188-mt6359: support dynamic pinctrl

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Message-ID: <b9e49c0a16bb59ed803fbb6102269b948be95ecc.camel@mediatek.com>
Date:   Wed, 26 Jul 2023 11:36:48 +0000
From:   Trevor Wu (吳文良) <Trevor.Wu@...iatek.com>
To:     "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "perex@...ex.cz" <perex@...ex.cz>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>
Subject: Re: [PATCH 1/3] ASoC: mediatek: mt8188-mt6359: support dynamic
 pinctrl

On Wed, 2023-07-26 at 08:43 +0200, AngeloGioacchino Del Regno wrote:
> Il 26/07/23 04:19, Trevor Wu (吳文良) ha scritto:
> > On Tue, 2023-07-25 at 09:06 +0200, AngeloGioacchino Del Regno
> > wrote:
> > > Il 25/07/23 05:53, Trevor Wu ha scritto:
> > > > To avoid power leakage, it is recommended to replace the
> > > > default
> > > > pinctrl
> > > > state with dynamic pinctrl since certain audio pinmux functions
> > > > can
> > > > remain in a HIGH state even when audio is disabled. Linking
> > > > pinctrl
> > > > with
> > > > DAPM using SND_SOC_DAPM_PINCTRL will ensure that audio pins
> > > > remain
> > > > in
> > > > GPIO mode by default and only switch to an audio function when
> > > > necessary.
> > > > 
> > > > Signed-off-by: Trevor Wu <trevor.wu@...iatek.com>
> > > > ---
> > > >    sound/soc/mediatek/mt8188/mt8188-mt6359.c | 21
> > > > +++++++++++++++++++++
> > > >    1 file changed, 21 insertions(+)
> > > > 
> > > > diff --git a/sound/soc/mediatek/mt8188/mt8188-mt6359.c
> > > > b/sound/soc/mediatek/mt8188/mt8188-mt6359.c
> > > > index 7c9e08e6a4f5..667d79f33bf2 100644
> > > > --- a/sound/soc/mediatek/mt8188/mt8188-mt6359.c
> > > > +++ b/sound/soc/mediatek/mt8188/mt8188-mt6359.c
> > > > @@ -246,6 +246,11 @@ static const struct snd_soc_dapm_widget
> > > > mt8188_mt6359_widgets[] = {
> > > >    	SND_SOC_DAPM_MIC("Headset Mic", NULL),
> > > >    	SND_SOC_DAPM_SINK("HDMI"),
> > > >    	SND_SOC_DAPM_SINK("DP"),
> > > > +
> > > > +	/* dynamic pinctrl */
> > > > +	SND_SOC_DAPM_PINCTRL("ETDM_SPK_PIN", "aud_etdm_spk_on",
> > > > "aud_etdm_spk_off"),
> > > > +	SND_SOC_DAPM_PINCTRL("ETDM_HP_PIN", "aud_etdm_hp_on",
> > > > "aud_etdm_hp_off"),
> > > > +	SND_SOC_DAPM_PINCTRL("MTKAIF_PIN", "aud_mtkaif_on",
> > > > "aud_mtkaif_off"),
> > > >    };
> > > >    
> > > >    static const struct snd_kcontrol_new
> > > > mt8188_mt6359_controls[] = {
> > > > @@ -267,6 +272,7 @@ static int
> > > > mt8188_mt6359_mtkaif_calibration(struct snd_soc_pcm_runtime
> > > > *rtd)
> > > >    		snd_soc_rtdcom_lookup(rtd, AFE_PCM_NAME);
> > > >    	struct snd_soc_component *cmpnt_codec =
> > > >    		asoc_rtd_to_codec(rtd, 0)->component;
> > > > +	struct snd_soc_dapm_widget *pin_w = NULL, *w;
> > > >    	struct mtk_base_afe *afe;
> > > >    	struct mt8188_afe_private *afe_priv;
> > > >    	struct mtkaif_param *param;
> > > > @@ -306,6 +312,18 @@ static int
> > > > mt8188_mt6359_mtkaif_calibration(struct snd_soc_pcm_runtime
> > > > *rtd)
> > > >    		return 0;
> > > >    	}
> > > >    
> > > > +	for_each_card_widgets(rtd->card, w) {
> > > > +		if (!strcmp(w->name, "MTKAIF_PIN")) {
> > > 
> > > if (strncmp(w->name, "MTKAIF_PIN", strlen(w->name) == 0) {
> > > 	pin_w = w;
> > > 	break;
> > > }
> > > 
> > > That's safer.
> > > 
> > 
> > If w->name is MTKAIF, the strncmp expression will return 0.
> > However,
> > the result is not expected. I prefer to keep strcmp here.
> > 
> 
> You could also do, instead
> 
> if (strncmp(w->name, "MTKAIF_PIN", strlen("MTKAIF_PIN") == 0))
> 
> ...solving your concern.
> 
> 

From my understanding, strncmp is utilized to determine a string begins
with a particular prefix while strcmp is used to compare a whole
string. In this scenario, I wish to verify if the widget name is
exactly 'MTKAIF_PIN', so I believe using strcmp would be more
appropriate.

Using either strlen(w->name) or strlen("MTKAIF_PIN") may lead to
incorrect results when w->name is either MTKAIF or MTKAIF_PIN1.

Thanks,
Trevor