Re: [PATCH] iio: Add Maxim MAX11100 driver

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On Tue, 6 Dec 2016, Jacopo Mondi wrote:

> Add IIO driver for Maxim MAX11100 single-channel ADC.
> Support raw_read mode only.

comments below; very minimal driver, but several easy issues...

the read_raw() is supposed to return millivolts (after application of 
offset and scale); maybe need _SCALE?
 
> Signed-off-by: Jacopo Mondi <jacopo@xxxxxxxxxx>
> ---
>  drivers/iio/adc/Kconfig    |   9 +++
>  drivers/iio/adc/Makefile   |   1 +
>  drivers/iio/adc/max11100.c | 165 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 175 insertions(+)
>  create mode 100644 drivers/iio/adc/max11100.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 99c0514..e2f3340 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -285,6 +285,15 @@ config MAX1027
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called max1027.
>  
> +config MAX11100
> +	tristate "Maxim max11100 ADC driver"
> +	depends on SPI
> +	help
> +	  Say yes here to build support for Maxim 11100 SPI ADC

Maxim max11100

> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called max11100.
> +
>  config MAX1363
>  	tristate "Maxim max1363 ADC driver"
>  	depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 7a40c04..1463044 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
>  obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
>  obj-$(CONFIG_LTC2485) += ltc2485.o
>  obj-$(CONFIG_MAX1027) += max1027.o
> +obj-$(CONFIG_MAX11100) += max11100.o
>  obj-$(CONFIG_MAX1363) += max1363.o
>  obj-$(CONFIG_MCP320X) += mcp320x.o
>  obj-$(CONFIG_MCP3422) += mcp3422.o
> diff --git a/drivers/iio/adc/max11100.c b/drivers/iio/adc/max11100.c
> new file mode 100644
> index 0000000..fbce287
> --- /dev/null
> +++ b/drivers/iio/adc/max11100.c
> @@ -0,0 +1,165 @@
> +/*
> + * iio/adc/max11100.c
> + * Maxim MAX11100 ADC Driver with IIO interface

MAX11100 or max11100

> + *
> + * Copyright (C) 2016 Renesas Electronics Corporation
> + * Copyright (C) 2016 Jacopo Mondi
> + *
> + * 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/kernel.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/delay.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> +
> +struct max11100_state {
> +	const struct max11100_chip_desc *desc;
> +	struct spi_device *spi;
> +	struct mutex lock;
> +};
> +
> +static struct iio_chan_spec max11100_channels[] = {
> +	{ /* [0] */
> +		.type = IIO_VOLTAGE,
> +		.channel = 0,

not indexed, so channel = 0 not needed

> +		.address = 0,

address not needed (and no need to initialize to 0 anyway)

> +		.scan_index = 0,

scan_index and scan_type not needed since no buffered support (yet); add 
this when needed

> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 16,
> +			.storagebits = 24,
> +			.shift = 8,
> +			.repeat = 1,
> +			.endianness = IIO_BE,
> +		},
> +		.output = 1,

no, ADC is typically not an output channel 

> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +	},
> +};
> +
> +static const unsigned long max11100_scan_masks[] = {

scan_masks not needed since no buffered support

> +	0xffff,
> +};
> +
> +static struct max11100_chip_desc {
> +	uint32_t num_chan;

why not just unsigned?

> +	const unsigned long *scanmasks;

not needed (yet)

> +	const struct iio_chan_spec *channels;
> +} max11100_desc = {
> +	.num_chan = 1,

ARRAY_SIZE(max11100_channels)

> +	.scanmasks = max11100_scan_masks,
> +	.channels = max11100_channels,
> +};
> +
> +static int max11100_read_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int *val, int *val2, long mask)
> +{
> +	int ret;
> +	struct max11100_state *state = iio_priv(indio_dev);
> +	uint8_t buffer[3] = { 0, 0, 0 };

no need to initialize buffer; consider alignment requirements for SPI

> +
> +	mutex_lock(&state->lock);

what is the mutex protecting?
must the spi_read() by protected? then the unlock can be placed right 
after the call...

> +
> +	ret = spi_read(state->spi, (void *) buffer, 3);

sizeof(buffer)

> +	if (ret) {
> +		dev_err(&indio_dev->dev, "SPI transfer failed\n");

mutex_unlock()!?

> +		return ret;
> +	}
> +
> +	dev_dbg(&indio_dev->dev, "ADC output values: "	\
> +		"[0]: 0x%2x [1]: 0x%2x [2]: 0x%2x\n",

probably 0x%02x if really needed

> +		buffer[0], buffer[1], buffer[2]);
> +
> +	/* the first 8 bits sent out from ADC must be 0s */
> +	if (buffer[0]) {
> +		dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n");

mutex_unlock()!?

> +		return -EINVAL;
> +	}
> +
> +	*val = (buffer[1] << 8) | buffer[2];
> +	mutex_unlock(&state->lock);
> +

shouldn't this return IIO_VAL_INT?

> +	return 0;
> +}
> +
> +static const struct iio_info max11100_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = max11100_read_raw,
> +};
> +
> +static int max11100_probe(struct spi_device *spi)
> +{
> +	int ret;
> +	struct iio_dev *indio_dev;
> +	struct max11100_state *state;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
> +	if (!indio_dev) {
> +		pr_err("Can't allocate iio device\n");

error message really needed?

> +		return -ENOMEM;
> +	}
> +	dev_dbg(&indio_dev->dev, "probe max11100 IIO SPI\n");

message really needed?

> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	state = iio_priv(indio_dev);
> +	state->spi = spi;
> +	state->desc = &max11100_desc;
> +
> +	mutex_init(&state->lock);
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->dev.of_node = spi->dev.of_node;
> +	indio_dev->info = &max11100_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = state->desc->channels;
> +	indio_dev->num_channels = state->desc->num_chan;
> +	indio_dev->available_scan_masks = state->desc->scanmasks;
> +
> +	ret = iio_device_register(indio_dev);

could use devm_ variant...

> +	if (ret) {
> +		dev_err(&indio_dev->dev, "Failed to register iio device\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int max11100_remove(struct spi_device *spi)

function not needed if using devm_iio_device_register()

> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +
> +	dev_dbg(&indio_dev->dev, "remove max11100 IIO SPI\n");
> +
> +	iio_device_unregister(indio_dev);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id max11100_ids[] = {
> +	{.compatible = "maxim,max11100"},
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, max11100_ids);
> +
> +static struct spi_driver max11100_driver = {
> +	.driver = {
> +		.name	= "max11100",
> +		.owner	= THIS_MODULE,
> +		.of_match_table = of_match_ptr(max11100_ids),
> +	},
> +	.probe		= max11100_probe,
> +	.remove		= max11100_remove,
> +};
> +
> +module_spi_driver(max11100_driver);
> +
> +MODULE_AUTHOR("Jacopo Mondi <jacopo@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Maxim MAX11100 ADC Driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald-Stadler
+43-664-2444418 (mobile)



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