linux-kernel - Re: [PATCH v4 2/2] iio: magnetometer: si7210: add driver for Si7210

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Message-ID: <Z4jCz1VXVPtEDNqB@smile.fi.intel.com>
Date: Thu, 16 Jan 2025 10:26:55 +0200
From: Andy Shevchenko <andy@...nel.org>
To: Antoni Pokusinski <apokusinski01@...il.com>
Cc: jic23@...nel.org, lars@...afoo.de, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, andrej.skvortzov@...il.com,
	neil.armstrong@...aro.org, icenowy@...c.io, megi@....cz,
	danila@...xyga.com, javier.carrasco.cruz@...il.com,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v4 2/2] iio: magnetometer: si7210: add driver for Si7210

On Wed, Jan 15, 2025 at 09:16:22PM +0100, Antoni Pokusinski wrote:
> Silicon Labs Si7210 is an I2C Hall effect magnetic position and
> temperature sensor. The driver supports the following functionalities:
> * reading the temperature measurements
> * reading the magnetic field measurements in a single-shot mode
> * choosing the magnetic field measurement scale (20 or 200 mT)

...

> +obj-$(CONFIG_SI7210) 			+= si7210.o

Looks like TAB/space mixture in the middle.

...

> +#include <asm/byteorder.h>

asm/* usually goes after linux/*

> +#include <linux/array_size.h>
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/cleanup.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/math64.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/mutex.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/types.h>
> +#include <linux/units.h>

...

Despite a good formatting I would still add a comment with a formula in
math-human-readable form.

> +		temp = FIELD_GET(GENMASK(14, 3), dspsig);
> +		temp = div_s64(-383 * temp * temp, 100) + 160940 * temp - 279800000;
> +		temp *= (1 + (data->temp_gain / 2048));
> +		temp += (int)(MICRO / 16) * data->temp_offset;

> +		ret = regulator_get_voltage(data->vdd);
> +		if (ret < 0)
> +			return ret;
> +
> +		temp -= 222 * div_s64(ret, MILLI);

Including this piece.

> +		*val = div_s64(temp, MILLI);

...

> +static int si7210_set_scale(struct si7210_data *data, unsigned int scale)
> +{
> +	s8 *a_otp_values;
> +	int ret;
> +
> +	if (scale == 20)
> +		a_otp_values = data->scale_20_a;
> +	else if (scale == 200)
> +		a_otp_values = data->scale_200_a;
> +	else
> +		return -EINVAL;
> +
> +	guard(mutex)(&data->fetch_lock);
> +
> +	/* Write the registers 0xCA - 0xCC */
> +	ret = regmap_bulk_write(data->regmap, SI7210_REG_A0, a_otp_values, 3);
> +	if (ret)
> +		return ret;

> +	/* Write the registers 0xCE - 0xD0 */
> +	ret = regmap_bulk_write(data->regmap, SI7210_REG_A3, &a_otp_values[3], 3);
> +	if (ret)
> +		return ret;

Just to be sure I understand the above. There are two of 24-bit values or there are
two sets of 3 byte arrays? How does datasheet refers to them? What does common sense
tell us here?

> +	data->curr_scale = scale;
> +
> +	return 0;
> +}

...

Overall LGTM, there is no need for resend as I believe the three things above
may be tweaked by Jonathan. The last one can go even if there are 2 24-bit
values, but ideally in that case we should use those as a such and apply
put_unaligned_be24/le24() whichever suits better.

-- 
With Best Regards,
Andy Shevchenko