linux-kernel - Re: [PATCH v7 01/14] ALSA: hda: hda_cs_dsp_ctl: Add Library to support CS

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Date:   Wed, 22 Jun 2022 10:40:20 +0200
From:   Amadeusz Sławiński 
        <amadeuszx.slawinski@...ux.intel.com>
To:     Vitaly Rodionov <vitalyr@...nsource.cirrus.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Mark Brown <broonie@...nel.org>
Cc:     patches@...nsource.cirrus.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org,
        Stefan Binding <sbinding@...nsource.cirrus.com>
Subject: Re: [PATCH v7 01/14] ALSA: hda: hda_cs_dsp_ctl: Add Library to
 support CS_DSP ALSA controls

On 6/22/2022 9:46 AM, Vitaly Rodionov wrote:
> From: Stefan Binding <sbinding@...nsource.cirrus.com>
> 
> The cs35l41 part contains a DSP which is able to run firmware.
> The cs_dsp library can be used to control the DSP.
> These controls can be exposed to userspace using ALSA controls.
> This library adds apis to be able to interface between
> cs_dsp and hda drivers and expose the relevant controls as
> ALSA controls.
> 
> Signed-off-by: Stefan Binding <sbinding@...nsource.cirrus.com>
> Signed-off-by: Vitaly Rodionov <vitalyr@...nsource.cirrus.com>
> ---
>   MAINTAINERS                    |   1 +
>   sound/pci/hda/Kconfig          |   4 +
>   sound/pci/hda/Makefile         |   2 +
>   sound/pci/hda/hda_cs_dsp_ctl.c | 207 +++++++++++++++++++++++++++++++++
>   sound/pci/hda/hda_cs_dsp_ctl.h |  33 ++++++
>   5 files changed, 247 insertions(+)
>   create mode 100644 sound/pci/hda/hda_cs_dsp_ctl.c
>   create mode 100644 sound/pci/hda/hda_cs_dsp_ctl.h
> 

...

> +
> +static unsigned int wmfw_convert_flags(unsigned int in)
> +{
> +	unsigned int out, rd, wr, vol;
> +
> +	rd = SNDRV_CTL_ELEM_ACCESS_READ;
> +	wr = SNDRV_CTL_ELEM_ACCESS_WRITE;
> +	vol = SNDRV_CTL_ELEM_ACCESS_VOLATILE;
> +
> +	out = 0;
> +
> +	if (in) {
> +		out |= rd;
> +		if (in & WMFW_CTL_FLAG_WRITEABLE)
> +			out |= wr;
> +		if (in & WMFW_CTL_FLAG_VOLATILE)
> +			out |= vol;
> +	} else {
> +		out |= rd | wr | vol;
> +	}
> +
> +	return out;
> +}

This is more question of preference, so you can leave above function as 
is, but you could also do something like the following, which is bit 
shorter:
static unsigned int wmfw_convert_flags(unsigned int in)
{
	unsigned int out = SNDRV_CTL_ELEM_ACCESS_READ;

	if (!in)
		return SNDRV_CTL_ELEM_ACCESS_READWRITE | SNDRV_CTL_ELEM_ACCESS_VOLATILE;

	if (in & WMFW_CTL_FLAG_WRITEABLE)
		out |= SNDRV_CTL_ELEM_ACCESS_WRITE;
	if (in & WMFW_CTL_FLAG_VOLATILE)
		out |= SNDRV_CTL_ELEM_ACCESS_VOLATILE;

	return out;
}

> +
> +static int hda_cs_dsp_add_kcontrol(struct hda_cs_dsp_coeff_ctl *ctl)
> +{
> +	struct cs_dsp_coeff_ctl *cs_ctl = ctl->cs_ctl;
> +	struct snd_kcontrol_new *kcontrol;
> +	struct snd_kcontrol *kctl;
> +	int ret = 0;
> +
> +	if (cs_ctl->len > ADSP_MAX_STD_CTRL_SIZE) {
> +		dev_err(cs_ctl->dsp->dev, "Control %s: length %zu exceeds maximum %d\n", ctl->name,
> +			cs_ctl->len, ADSP_MAX_STD_CTRL_SIZE);
> +		return -EINVAL;
> +	}
> +
> +	kcontrol = kzalloc(sizeof(*kcontrol), GFP_KERNEL);
> +	if (!kcontrol)
> +		return -ENOMEM;
> +
> +	kcontrol->name = ctl->name;
> +	kcontrol->info = hda_cs_dsp_coeff_info;
> +	kcontrol->iface = SNDRV_CTL_ELEM_IFACE_MIXER;
> +	kcontrol->private_value = (unsigned long)ctl;
> +	kcontrol->access = wmfw_convert_flags(cs_ctl->flags);
> +
> +	kcontrol->get = hda_cs_dsp_coeff_get;
> +	kcontrol->put = hda_cs_dsp_coeff_put;
> +
> +	kctl = snd_ctl_new1(kcontrol, NULL);

Wouldn't
kctl = snd_ctl_new1(kcontrol, ctl);
work instead of
kcontrol->private_value = (unsigned long)ctl;
...
kctl = snd_ctl_new1(kcontrol, NULL);
?

You can then get the value using  snd_kcontrol_chip()  macro, so instead 
of doing quite long lines with casts like:
struct hda_cs_dsp_coeff_ctl *ctl = (struct hda_cs_dsp_coeff_ctl 
*)kctl->private_value;
you could do
struct hda_cs_dsp_coeff_ctl *ctl = snd_kcontrol_chip(kctl);