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

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Date:   Wed, 26 Jul 2023 13:54:27 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Trevor Wu (吳文良) <Trevor.Wu@...iatek.com>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.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

Il 26/07/23 13:36, Trevor Wu (吳文良) ha scritto:
> 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

strcmp() and strncmp() are the same; except strncmp() compares *at most* `n` bytes,
where `n` is my `strlen("MTKAIF_PIN")`.

 From Linux man pages....
https://www.man7.org/linux/man-pages/man3/strcmp.3.html

Regards,
Angelo