linux-kernel - Re: [PATCH v3 6/6] iio: pressure: Add triggered buffer support for BMP280 driver

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Date: Wed, 20 Mar 2024 13:16:03 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Vasileios Amoiridis <vassilisamir@...il.com>
Cc: jic23@...nel.org, lars@...afoo.de, ang.iglesiasg@...il.com,
	mazziesaccount@...il.com, ak@...klinger.de,
	petre.rodan@...dimension.ro, phil@...pberrypi.com, 579lpy@...il.com,
	linus.walleij@...aro.org, semen.protsenko@...aro.org,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/6] iio: pressure: Add triggered buffer support for
 BMP280 driver

On Tue, Mar 19, 2024 at 01:29:25AM +0100, Vasileios Amoiridis wrote:
> BMP2xx, BMP3xx, and BMP5xx use consecutive buffers for their
> temperature, pressure and humidity readings. This facilitates
> the use of burst reads in order to acquire data much faster
> and in a different way from the one used in oneshot captures.
> 
> BMP085 and BMP180 use a completely different measurement
> process that is well defined and is used in their buffer_handler().

..

>  	ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
> -			       data->buf, sizeof(data->buf));
> +			       data->buf, BMP280_NUM_TEMP_BYTES);

>  	ret = regmap_bulk_read(data->regmap, BMP280_REG_PRESS_MSB,
> -			       data->buf, sizeof(data->buf));
> +			       data->buf, BMP280_NUM_PRESS_BYTES);

>  	ret = regmap_bulk_read(data->regmap, BMP280_REG_HUMIDITY_MSB,
> -			       &data->be16, sizeof(data->be16));
> +			       &data->be16, BME280_NUM_HUMIDITY_BYTES);

> -	adc_humidity = be16_to_cpu(data->be16);
> +	adc_humidity = get_unaligned_be16(&data->be16);

>  	ret = regmap_bulk_read(data->regmap, BMP380_REG_TEMP_XLSB,
> -			       data->buf, sizeof(data->buf));
> +			       data->buf, BMP280_NUM_TEMP_BYTES);

>  	ret = regmap_bulk_read(data->regmap, BMP380_REG_PRESS_XLSB,
> -			       data->buf, sizeof(data->buf));
> +			       data->buf, BMP280_NUM_PRESS_BYTES);

>  	ret = regmap_bulk_read(data->regmap, BMP580_REG_TEMP_XLSB, data->buf,
> -			       sizeof(data->buf));
> +			       BMP280_NUM_TEMP_BYTES);

>  	ret = regmap_bulk_read(data->regmap, BMP580_REG_PRESS_XLSB, data->buf,
> -			       sizeof(data->buf));
> +			       BMP280_NUM_PRESS_BYTES);

These smell to me as candidates to a separate patch with more explanation why.
(Yes, with the definitions you introduced.) But I leave it to Jonathan to
decide if we need to split.

..

The below are applicable to the bmp280_buffer_handler(),
bmp380_buffer_handler() implementations as well.

..

> +	/* Burst read data registers */
> +	ret = regmap_bulk_read(data->regmap, BMP580_REG_TEMP_XLSB,
> +			       data->buf, 6);

Magic size.

..

> +	/* Temperature calculations */
> +	memcpy(&chan_value, &data->buf[3], 3);

_le24() + sign_extend32()?

..

> +	/* Pressure calculations */
> +	memcpy(&chan_value, &data->buf[0], 3);

_le24() + sign_extend32()?

..

>  	/*
> -	 * Maximum number of consecutive bytes read for a temperature or
> -	 * pressure measurement is 3.
> +	 * Maximum number of a burst read for temperature, pressure, humidity
> +	 * is 8 bytes.
>  	 */
> -	if (val_size > 3)
> +	if (val_size > 8)

sizeof() / new definition for the buf[] size?

>  		return -EINVAL;

-- 
With Best Regards,
Andy Shevchenko