linux-kernel - Re: [PATCH v2 2/5] iio: pressure: bmp280: Add preinit callback

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Date:   Fri, 30 Dec 2022 18:18:39 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Angel Iglesias <ang.iglesiasg@...il.com>
Cc:     linux-iio@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Paul Cercueil <paul@...pouillou.net>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Andreas Klinger <ak@...klinger.de>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] iio: pressure: bmp280: Add preinit callback

On Mon, 26 Dec 2022 15:29:21 +0100
Angel Iglesias <ang.iglesiasg@...il.com> wrote:

> Adds preinit callback to execute operations on probe before applying
> initial configuration.
> 
> Signed-off-by: Angel Iglesias <ang.iglesiasg@...il.com>
> 
> diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
> index 46959a91408f..c37cf2caec68 100644
> --- a/drivers/iio/pressure/bmp280-core.c
> +++ b/drivers/iio/pressure/bmp280-core.c
> @@ -217,6 +217,7 @@ struct bmp280_chip_info {
>  	int (*read_press)(struct bmp280_data *, int *, int *);
>  	int (*read_humid)(struct bmp280_data *, int *, int *);
>  	int (*read_calib)(struct bmp280_data *);
> +	int (*preinit)(struct bmp280_data *);
>  };
>  
>  /*
> @@ -935,6 +936,7 @@ static const struct bmp280_chip_info bmp280_chip_info = {
>  	.read_temp = bmp280_read_temp,
>  	.read_press = bmp280_read_press,
>  	.read_calib = bmp280_read_calib,
> +	.preinit = NULL,
C standard guarantees those are set to NULL anyway + the default is obvious.
Hence don't set them to NULL, just leave the automatic initialization of
unspecified structure elements to handle it for you.

>  };
>  
>  static int bme280_chip_config(struct bmp280_data *data)
> @@ -979,6 +981,7 @@ static const struct bmp280_chip_info bme280_chip_info = {
>  	.read_press = bmp280_read_press,
>  	.read_humid = bmp280_read_humid,
>  	.read_calib = bme280_read_calib,
> +	.preinit = NULL,
>  };
>  
>  /*
> @@ -1220,6 +1223,12 @@ static const int bmp380_odr_table[][2] = {
>  	[BMP380_ODR_0_0015HZ]	= {0, 1526},
>  };
>  
> +static int bmp380_preinit(struct bmp280_data *data)
> +{
> +	/* BMP3xx requires soft-reset as part of initialization */
> +	return bmp380_cmd(data, BMP380_CMD_SOFT_RESET);
> +}
> +
>  static int bmp380_chip_config(struct bmp280_data *data)
>  {
>  	bool change = false, aux;
> @@ -1349,6 +1358,7 @@ static const struct bmp280_chip_info bmp380_chip_info = {
>  	.read_temp = bmp380_read_temp,
>  	.read_press = bmp380_read_press,
>  	.read_calib = bmp380_read_calib,
> +	.preinit = bmp380_preinit,
>  };
>  
>  static int bmp180_measure(struct bmp280_data *data, u8 ctrl_meas)
> @@ -1604,6 +1614,7 @@ static const struct bmp280_chip_info bmp180_chip_info = {
>  	.read_temp = bmp180_read_temp,
>  	.read_press = bmp180_read_press,
>  	.read_calib = bmp180_read_calib,
> +	.preinit = NULL,
>  };
>  
>  static irqreturn_t bmp085_eoc_irq(int irq, void *d)
> @@ -1762,9 +1773,13 @@ int bmp280_common_probe(struct device *dev,
>  		return -EINVAL;
>  	}
>  
> -	/* BMP3xx requires soft-reset as part of initialization */
> -	if (chip_id == BMP380_CHIP_ID) {
> -		ret = bmp380_cmd(data, BMP380_CMD_SOFT_RESET);
> +	/*
> +	 * Some chips like the BMP3xx have preinit tasks to run
> +	 * before applying the initial configuration.
> +	 */
I would drop this comment. It's kind of obvious that some devices need you
to call something here - otherwise why have the clearly optional callback?
The specific BMP3xx requirements are well commented in your new callback above
so don't want to be here as well.

> +	if (data->chip_info->preinit) {
> +		ret = data->chip_info->preinit(data);
> +		dev_err(dev, "error running preinit tasks");

Error message printed on success...

>  		if (ret < 0)
>  			return ret;

			return dev_err_probe(dev, ret, "error running preinit tasks");

>  	}