linux-kernel - Re: [PATCH 1/2] ASoC: codec: wcd938x: Add switch control for selecting CTIA/OMTP Headset

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Date:   Mon, 14 Feb 2022 13:47:17 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Srinivasa Rao Mandadapu <quic_srivasam@...cinc.com>,
        agross@...nel.org, alsa-devel@...a-project.org,
        bgoswami@...eaurora.org, bjorn.andersson@...aro.org,
        broonie@...nel.org, devicetree@...r.kernel.org,
        judyhsiao@...omium.org, lgirdwood@...il.com,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        perex@...ex.cz, quic_plai@...cinc.com, robh+dt@...nel.org,
        rohitkr@...eaurora.org, srinivas.kandagatla@...aro.org,
        tiwai@...e.com
Cc:     Venkata Prasad Potturu <quic_potturu@...cinc.com>
Subject: Re: [PATCH 1/2] ASoC: codec: wcd938x: Add switch control for
 selecting CTIA/OMTP Headset

Quoting Srinivasa Rao Mandadapu (2022-02-12 04:24:31)
> diff --git a/sound/soc/codecs/wcd938x.c b/sound/soc/codecs/wcd938x.c
> index eff200a..08d16a9 100644
> --- a/sound/soc/codecs/wcd938x.c
> +++ b/sound/soc/codecs/wcd938x.c
> @@ -194,6 +194,7 @@ struct wcd938x_priv {
>         int ear_rx_path;
>         int variant;
>         int reset_gpio;
> +       int us_euro_gpio;
>         u32 micb1_mv;
>         u32 micb2_mv;
>         u32 micb3_mv;
> @@ -4196,6 +4197,33 @@ static void wcd938x_dt_parse_micbias_info(struct device *dev, struct wcd938x_pri
>                 dev_info(dev, "%s: Micbias4 DT property not found\n", __func__);
>  }
>
> +static bool wcd938x_swap_gnd_mic(struct snd_soc_component *component, bool active)
> +{
> +       int value;
> +
> +       struct wcd938x_priv *wcd938x;
> +
> +       if (!component) {

So component is NULL

> +               dev_err(component->dev, "%s component is NULL\n", __func__);

And now we deref component. Great NULL pointer exception Batman! Please
test your code and remove useless checks. It makes the code harder to
read and slows things down.

> +               return false;
> +       }
> +
> +       wcd938x = snd_soc_component_get_drvdata(component);
> +       if (!wcd938x) {
> +               dev_err(component->dev, "%s private data is NULL\n", __func__);

Is this possible? I doubt it so can we just remove it?

> +               return false;
> +       }
> +
> +       value = gpio_get_value(wcd938x->us_euro_gpio);
> +
> +       gpio_set_value(wcd938x->us_euro_gpio, !value);
> +       /* 20us sleep required after changing the gpio state*/

Add a space before ending comment with */

> +       usleep_range(20, 30);
> +
> +       return true;
> +}
> +
> +
>  static int wcd938x_populate_dt_data(struct wcd938x_priv *wcd938x, struct device *dev)
>  {
>         struct wcd_mbhc_config *cfg = &wcd938x->mbhc_cfg;
> @@ -4208,6 +4236,16 @@ static int wcd938x_populate_dt_data(struct wcd938x_priv *wcd938x, struct device
>                 return wcd938x->reset_gpio;
>         }
>
> +       wcd938x->us_euro_gpio = of_get_named_gpio(dev->of_node, "us-euro-gpios", 0);

Why do we need to use of GPIO APIs here? Can this driver be converted to
use GPIO descriptors via the gpiod APIs?

> +       if (wcd938x->us_euro_gpio < 0) {
> +               dev_err(dev, "Failed to get us-euro-gpios gpio: err = %d\n", wcd938x->us_euro_gpio);
> +       } else {
> +               cfg->swap_gnd_mic = wcd938x_swap_gnd_mic;
> +               gpio_direction_output(wcd938x->us_euro_gpio, 0);
> +               /* 20us sleep required after pulling the reset gpio to LOW */
> +               usleep_range(20, 30);
> +       }
> +