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Date:	Sat, 21 May 2016 20:14:11 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Cristina Moraru <cristina.moraru09@...il.com>, knaack.h@....de,
	lars@...afoo.de, pmeerw@...erw.net, sst@...zta.fm, peda@...ntia.se,
	mranostay@...il.com, manabian@...il.com,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	daniel.baluta@...el.com, octavian.purdila@...el.com
Subject: Re: [PATCH v5] iio: max5487: Add support for Maxim digital
 potentiometers

On 19/05/16 06:55, Cristina Moraru wrote:
> Add implementation for Maxim MAX5487, MAX5488, MAX5489
> digital potentiometers.
> 
> Datasheet:
> http://datasheets.maximintegrated.com/en/ds/MAX5487-MAX5489.pdf
> 
> Signed-off-by: Cristina Moraru <cristina.moraru09@...il.com>
> CC: Daniel Baluta <daniel.baluta@...el.com>
Applied to the togreg branch of iio.git - initially pushed out as
testing.  As ever with stuff in testing I can still modify the
commit if anyone has anything to add (acks etc welcome of course!)

Jonathan
> ---
> Changes since v4:
> 	Add year for copyright
> Changes since v3:
>         Fix size issue in max5487_write_cmd
>         Fix typo
> Changes since v2:
>         Change switch statement in max5487_write_raw
>         to if statement for consistency
>         Add blank line before return statement
>         Eliminate regmap support and use spi_write
>         Use iio_device_register instead of devm_ version
> Changes since v1:
>         Fix spacing
>         Eliminate max5487_cfg struct
>         Add kohms as driver data
> 
>  drivers/iio/potentiometer/Kconfig   |  11 +++
>  drivers/iio/potentiometer/Makefile  |   1 +
>  drivers/iio/potentiometer/max5487.c | 161 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 173 insertions(+)
>  create mode 100644 drivers/iio/potentiometer/max5487.c
> 
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index 6acb238..0941c8d4 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -15,6 +15,17 @@ config DS1803
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ds1803.
>  
> +config MAX5487
> +        tristate "Maxim MAX5487/MAX5488/MAX5489 Digital Potentiometer driver"
> +        depends on SPI
> +        help
> +          Say yes here to build support for the Maxim
> +          MAX5487, MAX5488, MAX5489 digital potentiometer
> +          chips.
> +
> +          To compile this driver as a module, choose M here: the
> +          module will be called max5487.
> +
>  config MCP4131
>  	tristate "Microchip MCP413X/414X/415X/416X/423X/424X/425X/426X Digital Potentiometer driver"
>  	depends on SPI
> diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
> index 6007faa..8adb58f 100644
> --- a/drivers/iio/potentiometer/Makefile
> +++ b/drivers/iio/potentiometer/Makefile
> @@ -4,6 +4,7 @@
>  
>  # When adding new entries keep the list in alphabetical order
>  obj-$(CONFIG_DS1803) += ds1803.o
> +obj-$(CONFIG_MAX5487) += max5487.o
>  obj-$(CONFIG_MCP4131) += mcp4131.o
>  obj-$(CONFIG_MCP4531) += mcp4531.o
>  obj-$(CONFIG_TPL0102) += tpl0102.o
> diff --git a/drivers/iio/potentiometer/max5487.c b/drivers/iio/potentiometer/max5487.c
> new file mode 100644
> index 0000000..6c50939
> --- /dev/null
> +++ b/drivers/iio/potentiometer/max5487.c
> @@ -0,0 +1,161 @@
> +/*
> + * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers
> + *
> + * Copyright (C) 2016 Cristina-Gabriela Moraru <cristina.moraru09@...il.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/acpi.h>
> +
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/iio.h>
> +
> +#define MAX5487_WRITE_WIPER_A	(0x01 << 8)
> +#define MAX5487_WRITE_WIPER_B	(0x02 << 8)
> +
> +/* copy both wiper regs to NV regs */
> +#define MAX5487_COPY_AB_TO_NV	(0x23 << 8)
> +/* copy both NV regs to wiper regs */
> +#define MAX5487_COPY_NV_TO_AB	(0x33 << 8)
> +
> +#define MAX5487_MAX_POS		255
> +
> +struct max5487_data {
> +	struct spi_device *spi;
> +	int kohms;
> +};
> +
> +#define MAX5487_CHANNEL(ch, addr) {				\
> +	.type = IIO_RESISTANCE,					\
> +	.indexed = 1,						\
> +	.output = 1,						\
> +	.channel = ch,						\
> +	.address = addr,					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +}
> +
> +static const struct iio_chan_spec max5487_channels[] = {
> +	MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),
> +	MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),
> +};
> +
> +static int max5487_write_cmd(struct spi_device *spi, u16 cmd)
> +{
> +	return spi_write(spi, (const void *) &cmd, sizeof(u16));
> +}
> +
> +static int max5487_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct max5487_data *data = iio_priv(indio_dev);
> +
> +	if (mask != IIO_CHAN_INFO_SCALE)
> +		return -EINVAL;
> +
> +	*val = 1000 * data->kohms;
> +	*val2 = MAX5487_MAX_POS;
> +
> +	return IIO_VAL_FRACTIONAL;
> +}
> +
> +static int max5487_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val, int val2, long mask)
> +{
> +	struct max5487_data *data = iio_priv(indio_dev);
> +
> +	if (mask != IIO_CHAN_INFO_RAW)
> +		return -EINVAL;
> +
> +	if (val < 0 || val > MAX5487_MAX_POS)
> +		return -EINVAL;
> +
> +	return max5487_write_cmd(data->spi, chan->address | val);
> +}
> +
> +static const struct iio_info max5487_info = {
> +	.read_raw = max5487_read_raw,
> +	.write_raw = max5487_write_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int max5487_spi_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct max5487_data *data;
> +	const struct spi_device_id *id = spi_get_device_id(spi);
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(&spi->dev, indio_dev);
> +	data = iio_priv(indio_dev);
> +
> +	data->spi = spi;
> +	data->kohms = id->driver_data;
> +
> +	indio_dev->info = &max5487_info;
> +	indio_dev->name = id->name;
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = max5487_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(max5487_channels);
> +
> +	/* restore both wiper regs from NV regs */
> +	ret = max5487_write_cmd(data->spi, MAX5487_COPY_NV_TO_AB);
> +	if (ret < 0)
> +		return ret;
> +
> +	return iio_device_register(indio_dev);
> +}
> +
> +static int max5487_spi_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	/* save both wiper regs to NV regs */
> +	return max5487_write_cmd(spi, MAX5487_COPY_AB_TO_NV);
> +}
> +
> +static const struct spi_device_id max5487_id[] = {
> +	{ "MAX5487", 10 },
> +	{ "MAX5488", 50 },
> +	{ "MAX5489", 100 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(spi, max5487_id);
> +
> +static const struct acpi_device_id max5487_acpi_match[] = {
> +	{ "MAX5487", 10 },
> +	{ "MAX5488", 50 },
> +	{ "MAX5489", 100 },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);
> +
> +static struct spi_driver max5487_driver = {
> +	.driver = {
> +		.name = "max5487",
> +		.owner = THIS_MODULE,
> +		.acpi_match_table = ACPI_PTR(max5487_acpi_match),
> +	},
> +	.id_table = max5487_id,
> +	.probe = max5487_spi_probe,
> +	.remove = max5487_spi_remove
> +};
> +module_spi_driver(max5487_driver);
> +
> +MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@...il.com>");
> +MODULE_DESCRIPTION("max5487 SPI driver");
> +MODULE_LICENSE("GPL v2");
> 

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