Re: [PATCH v4 6/6] iio: adc: ad4851: add ad485x driver

[Jonathan Cameron <jic23@xxxxxxxxxx>]

On Fri, 18 Oct 2024 13:42:10 +0300
Antoniu Miclaus <antoniu.miclaus@xxxxxxxxxx> wrote:

> Add support for the AD485X a fully buffered, 8-channel simultaneous
> sampling, 16/20-bit, 1 MSPS data acquisition system (DAS) with
> differential, wide common-mode range inputs.
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@xxxxxxxxxx>

A few minor things from me that I could fix whilst applying,
but David gave a much more detailed review of v3, so I'll wait
for his feedback on this.  I haven't dug into datasheets much and
may well have missed other things.

>  obj-$(CONFIG_AD7091R8) += ad7091r8.o
> diff --git a/drivers/iio/adc/ad4851.c b/drivers/iio/adc/ad4851.c
> new file mode 100644
> index 000000000000..65aa434b535f
> --- /dev/null
> +++ b/drivers/iio/adc/ad4851.c
> @@ -0,0 +1,1155 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Analog Devices AD4851 DAS driver
> + *
> + * Copyright 2024 Analog Devices Inc.
> + */
> +
> +#include <linux/array_size.h>
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/minmax.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +#include <linux/types.h>
> +#include <linux/units.h>
> +
> +#include <linux/iio/backend.h>
> +#include <linux/iio/iio.h>
> +
> +#include <asm/unaligned.h>
This moved. I can fix up whilst applying but it is now at linux/unaligned.h
as of rc2.



> +static int ad4851_get_calibscale(struct ad4851_state *st, int ch, int *val, int *val2)
> +{
> +	unsigned int reg_val;
> +	int gain;
> +	int ret;
> +
> +	guard(mutex)(&st->lock);
> +
> +	ret = regmap_read(st->regmap, AD4851_REG_CHX_GAIN_MSB(ch),
> +			  &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	gain = (reg_val & 0xFF) << 8;

The register size is 8 bits, so I'm not sure what that masking is adding.
	gain = reg_val << 8; should be fine.  Maybe the compiler or some
static analysis is wrong?

> +
> +	ret = regmap_read(st->regmap, AD4851_REG_CHX_GAIN_LSB(ch),
> +			  &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	gain |= reg_val & 0xFF;

same here.

> +
> +	*val = gain;
> +	*val2 = 32768;
> +
> +	return IIO_VAL_FRACTIONAL;
> +}
> +