linux-kernel - Re: [PATCH] gnss: Use devm_regulator_get_enable

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Message-ID: <ZJFqCQ8bbBoX3l1g@hovoldconsulting.com>
Date:   Tue, 20 Jun 2023 10:57:45 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] gnss: Use devm_regulator_get_enable_optional()

On Sat, Jun 17, 2023 at 11:57:09AM +0200, Christophe JAILLET wrote:
> Use devm_regulator_get_enable_optional() instead of hand writing it. It
> saves some line of code.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> Note that regulator_disable() is now called after gnss_serial_free() in
> the error handling path of the probe and in the remove function, but it
> looks harmless to me.

Yeah, that bit should be fine.

> ---
>  drivers/gnss/mtk.c | 26 ++++----------------------
>  1 file changed, 4 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gnss/mtk.c b/drivers/gnss/mtk.c
> index c62b1211f4fe..d3d31295d4e0 100644
> --- a/drivers/gnss/mtk.c
> +++ b/drivers/gnss/mtk.c
> @@ -17,7 +17,6 @@
>  #include "serial.h"
>  
>  struct mtk_data {
> -	struct regulator *vbackup;
>  	struct regulator *vcc;
>  };
>  
> @@ -87,30 +86,16 @@ static int mtk_probe(struct serdev_device *serdev)
>  		goto err_free_gserial;
>  	}
>  
> -	data->vbackup = devm_regulator_get_optional(&serdev->dev, "vbackup");
> -	if (IS_ERR(data->vbackup)) {
> -		ret = PTR_ERR(data->vbackup);
> -		if (ret == -ENODEV)
> -			data->vbackup = NULL;
> -		else
> -			goto err_free_gserial;
> -	}
> -
> -	if (data->vbackup) {
> -		ret = regulator_enable(data->vbackup);
> -		if (ret)
> -			goto err_free_gserial;
> -	}
> +	ret = devm_regulator_get_enable_optional(&serdev->dev, "vbackup");
> +	if (ret)
> +		goto err_free_gserial;

But this breaks the driver as the new helper still returns -ENODEV when
the optional is resource is not present.

Wolfram already suggested using this new helper here:

	https://lore.kernel.org/lkml/20230523064310.3005-3-wsa+renesas@sang-engineering.com

and also got the error handling right even if that patch will require a
respin for other reasons.

As I mentioned in my reply to Wolfram, I'm generally sceptical of
helpers like this one, but in this case where there are no dependencies
on other resources I guess it's ok.

Johan