linux-kernel - Re: [PATCH v2 2/3] ASoC: starfive: Add JH7110 PWM-DAC driver

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Date:   Mon, 31 Jul 2023 20:14:38 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Hal Feng <hal.feng@...rfivetech.com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Walker Chen <walker.chen@...rfivetech.com>,
        Xingyu Wu <xingyu.wu@...rfivetech.com>,
        Emil Renner Berthing <emil.renner.berthing@...onical.com>,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] ASoC: starfive: Add JH7110 PWM-DAC driver

On Mon, Jul 31, 2023 at 11:28:28AM +0800, Hal Feng wrote:

> +static const struct jh7110_ct_pwmdac pwmdac_ct_data_shift[] = {
> +	{ .name = "left 0 bit", .vals = PWMDAC_DATA_LEFT_SHIFT_BIT_0 },
> +	{ .name = "left 1 bit", .vals = PWMDAC_DATA_LEFT_SHIFT_BIT_1 },
> +	{ .name = "left 2 bit", .vals = PWMDAC_DATA_LEFT_SHIFT_BIT_2 },
> +	{ .name = "left 3 bit", .vals = PWMDAC_DATA_LEFT_SHIFT_BIT_3 },
> +	{ .name = "left 4 bit", .vals = PWMDAC_DATA_LEFT_SHIFT_BIT_4 },
> +	{ .name = "left 5 bit", .vals = PWMDAC_DATA_LEFT_SHIFT_BIT_5 },
> +	{ .name = "left 6 bit", .vals = PWMDAC_DATA_LEFT_SHIFT_BIT_6 },
> +	{ .name = "left 7 bit", .vals = PWMDAC_DATA_LEFT_SHIFT_BIT_7 }
> +};

It's not clear to me why this is user selectable - what does the control
do?

> +static int jh7110_pwmdac_put(struct snd_kcontrol *kcontrol,
> +			     struct snd_ctl_elem_value *ucontrol,
> +			     int pwmdac_ct)
> +{
> +	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
> +	struct jh7110_pwmdac_dev *dev = snd_soc_component_get_drvdata(component);
> +	int sel = ucontrol->value.enumerated.item[0];
> +	unsigned int items;

> +	if (pwmdac_ct == PWMDAC_CT_SHIFT)
> +		dev->shift = pwmdac_ct_shift[sel].vals;
> +	else if (pwmdac_ct == PWMDAC_CT_DUTY_CYCLE)
> +		dev->duty_cycle = pwmdac_ct_duty_cycle[sel].vals;
> +	else if (pwmdac_ct == PWMDAC_CT_DATA_CHANGE)
> +		dev->data_change = pwmdac_ct_data_change[sel].vals;
> +	else if (pwmdac_ct == PWMDAC_CT_DATA_MODE)
> +		dev->data_mode = pwmdac_ct_data_mode[sel].vals;
> +	else if (pwmdac_ct == PWMDAC_CT_DATA_SHIFT)
> +		dev->data_shift = pwmdac_ct_data_shift[sel].vals;
> +
> +	return 0;
> +}

_put() operations should return 1 if the control value changes so event
generation works - please test a card using this driver with the
mixer-test selftest, it'll identify this and a bunch of other potential
issues.

> +static int jh7110_pwmdac_component_probe(struct snd_soc_component *component)
> +{
> +	snd_soc_add_component_controls(component, jh7110_pwmdac_snd_controls,
> +				       ARRAY_SIZE(jh7110_pwmdac_snd_controls));
> +	return 0;
> +}

The driver can just point to the controls from the _driver struct and
skip having a probe() function.


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