Message-ID: <538CBF50.8080603@kernel.org>
Date:	Mon, 02 Jun 2014 19:15:44 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Philippe Reynes <tremyfr@...oo.fr>, linux-iio@...r.kernel.org
CC:	linux-kernel@...r.kernel.org, armadeus-forum@...ts.sourceforge.net,
	knaack.h@....de, lars@...afoo.de, devicetree@...r.kernel.org
Subject: Re: [PATCH v4] iio: add support of the max1027

On 31/05/14 22:47, Philippe Reynes wrote:
> This driver add partial support of the
> maxim 1027/1029/1031. Differential mode is not
> supported.
>
> It was tested on armadeus apf27 board.
>
> Signed-off-by: Philippe Reynes <tremyfr@...oo.fr>
Hi Philippe,

A couple of bits have snuck in (sorry, I missed them when I looked
at it the other day!).

1) No need to type case parameters to (void *).
2) Your spi_write calls are, sometimes at least, using data on the
    stack. The spi subsystem can use these buffers directly for dma.  As such
    you need to carefully ensure then don't share a cache line with anything
    else. The easy way to do this is to use a buffer allocated on it's own
    on the heap.  There are tricks to doing it within a structure allocated
    on the heap as well.

Once you have those two bits cleaned up, I'd like to give Harmutt a chance
to comment / give a reviewed-by.  Right now we are looking at a merge
in the next kernel cycle anyway so have masses of time.

J
> ---
>   .../devicetree/bindings/iio/adc/max1027-adc.txt    |   22 +
>   drivers/iio/adc/Kconfig                            |    9 +
>   drivers/iio/adc/Makefile                           |    1 +
>   drivers/iio/adc/max1027.c                          |  506 ++++++++++++++++++++
>   4 files changed, 538 insertions(+), 0 deletions(-)
>   create mode 100644 Documentation/devicetree/bindings/iio/adc/max1027-adc.txt
>   create mode 100644 drivers/iio/adc/max1027.c
>
> Changelog:
> v4: (thanks Jonathan Cameron for the feedback)
> - use iio_trigger_generic_data_rdy_poll
>
> v3: (thanks Hartmut Knaack, Lars-Peter Clausen and Jonathan Cameron for the feedback)
> - move to drivers/iio/adc (was in staging)
> - clean binding doc
> - drop empty update_scan_mode callback
> - add a lock around single channel read code
> - remove useless wrappers around spi_write and spi_read
> - fix available scan mask (a bit was missing)
> - remove useless header
> - some others little cleanp
>
> v2: (thanks Hartmut Knaack and Jonathan Cameron for the feedback)
> - really use devm_*
> - use demux magic
> - use spi_read and spi_write (instead of spi_sync)
> - use define for register (instead of hardcoded value)
>
> diff --git a/Documentation/devicetree/bindings/iio/adc/max1027-adc.txt b/Documentation/devicetree/bindings/iio/adc/max1027-adc.txt
> new file mode 100644
> index 0000000..a8770cc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/max1027-adc.txt
> @@ -0,0 +1,22 @@
> +* Maxim 1027/1029/1031 Analog to Digital Converter (ADC)
> +
> +Required properties:
> +  - compatible: Should be "maxim,max1027" or "maxim,max1029" or "maxim,max1031"
> +  - reg: SPI chip select number for the device
> +  - interrupt-parent: phandle to the parent interrupt controller
> +  see: Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
> +  - interrupts: IRQ line for the ADC
> +  see: Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
> +
> +Recommended properties:
> +- spi-max-frequency: Definition as per
> +                     Documentation/devicetree/bindings/spi/spi-bus.txt
> +
> +Example:
> +adc@0 {
> +	compatible = "maxim,max1027";
> +	reg = <0>;
> +	interrupt-parent = <&gpio5>;
> +	interrupts = <15 IRQ_TYPE_EDGE_RISING>;
> +	spi-max-frequency = <1000000>;
> +};
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 24c28e3..517f886 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -119,6 +119,15 @@ config LP8788_ADC
>   	help
>   	  Say yes here to build support for TI LP8788 ADC.
>
> +config MAX1027
> +	tristate "Maxim max1027 ADC driver"
> +	depends on SPI
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +	help
> +	  Say yes here to build support for Maxim SPI ADC models
> +	  max1027, max1029 and max1031.
> +
>   config MAX1363
>   	tristate "Maxim max1363 ADC driver"
>   	depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index ab346d8..daac784 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_AD7887) += ad7887.o
>   obj-$(CONFIG_AT91_ADC) += at91_adc.o
>   obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
>   obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
> +obj-$(CONFIG_MAX1027) += max1027.o
>   obj-$(CONFIG_MAX1363) += max1363.o
>   obj-$(CONFIG_MCP320X) += mcp320x.o
>   obj-$(CONFIG_MCP3422) += mcp3422.o
> diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> new file mode 100644
> index 0000000..6c2cb88
> --- /dev/null
> +++ b/drivers/iio/adc/max1027.c
> @@ -0,0 +1,506 @@
> + /*
> +  * iio/adc/max1027.c
> +  * Copyright (C) 2014 Philippe Reynes
> +  *
> +  * based on linux/drivers/iio/ad7923.c
> +  * Copyright 2011 Analog Devices Inc (from AD7923 Driver)
> +  * Copyright 2012 CS Systemes d'Information
> +  *
> +  * 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.
> +  *
> +  * max1027.c
> +  *
> +  * Partial support for max1027 and similar chips.
> +  */
> +
> +#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>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +
> +#define MAX1027_CONV_REG  0x80
> +#define MAX1027_SETUP_REG 0x40
> +#define MAX1027_AVG_REG   0x20
> +#define MAX1027_RST_REG   0x10
> +
> +/* conversion register */
> +#define MAX1027_TEMP      0x01
> +#define MAX1027_SCAN_0_N  (0x00 << 1)
> +#define MAX1027_SCAN_N_M  (0x01 << 1)
> +#define MAX1027_SCAN_N    (0x02 << 1)
> +#define MAX1027_NOSCAN    (0x03 << 1)
> +#define MAX1027_CHAN(n)   ((n) << 3)
> +
> +/* setup register */
> +#define MAX1027_UNIPOLAR  0x02
> +#define MAX1027_BIPOLAR   0x03
> +#define MAX1027_REF_MODE0 (0x00 << 2)
> +#define MAX1027_REF_MODE1 (0x01 << 2)
> +#define MAX1027_REF_MODE2 (0x02 << 2)
> +#define MAX1027_REF_MODE3 (0x03 << 2)
> +#define MAX1027_CKS_MODE0 (0x00 << 4)
> +#define MAX1027_CKS_MODE1 (0x01 << 4)
> +#define MAX1027_CKS_MODE2 (0x02 << 4)
> +#define MAX1027_CKS_MODE3 (0x03 << 4)
> +
> +/* averaging register */
> +#define MAX1027_NSCAN_4   0x00
> +#define MAX1027_NSCAN_8   0x01
> +#define MAX1027_NSCAN_12  0x02
> +#define MAX1027_NSCAN_16  0x03
> +#define MAX1027_NAVG_4    (0x00 << 2)
> +#define MAX1027_NAVG_8    (0x01 << 2)
> +#define MAX1027_NAVG_16   (0x02 << 2)
> +#define MAX1027_NAVG_32   (0x03 << 2)
> +#define MAX1027_AVG_EN    (0x01 << 4)
> +
> +enum max1027_id {
> +	max1027,
> +	max1029,
> +	max1031,
> +};
> +
> +static const struct spi_device_id max1027_id[] = {
> +	{"max1027", max1027},
> +	{"max1029", max1029},
> +	{"max1031", max1031},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, max1027_id);
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id max1027_adc_dt_ids[] = {
> +	{ .compatible = "maxim,max1027" },
> +	{ .compatible = "maxim,max1029" },
> +	{ .compatible = "maxim,max1031" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, max1027_adc_dt_ids);
> +#endif
> +
> +#define MAX1027_V_CHAN(index)						\
> +	{								\
> +		.type = IIO_VOLTAGE,					\
> +		.indexed = 1,						\
> +		.channel = index,					\
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +		.scan_index = index+1,					\
> +		.scan_type = {						\
> +			.sign = 'u',					\
> +			.realbits = 10,					\
> +			.storagebits = 16,				\
> +			.shift = 2,					\
> +			.endianness = IIO_BE,				\
> +		},							\
> +	}
> +
> +#define MAX1027_T_CHAN(index)						\
> +	{								\
> +		.type = IIO_TEMP,					\
> +		.channel = index,					\
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +		.scan_index = index,					\
> +		.scan_type = {						\
> +			.sign = 'u',					\
> +			.realbits = 12,					\
> +			.storagebits = 16,				\
> +			.endianness = IIO_BE,				\
> +		},							\
> +	}
> +
> +static const struct iio_chan_spec max1027_channels[] = {
> +	MAX1027_T_CHAN(0),
> +	MAX1027_V_CHAN(0),
> +	MAX1027_V_CHAN(1),
> +	MAX1027_V_CHAN(2),
> +	MAX1027_V_CHAN(3),
> +	MAX1027_V_CHAN(4),
> +	MAX1027_V_CHAN(5),
> +	MAX1027_V_CHAN(6),
> +	MAX1027_V_CHAN(7)
> +};
> +
> +static const struct iio_chan_spec max1029_channels[] = {
> +	MAX1027_T_CHAN(0),
> +	MAX1027_V_CHAN(0),
> +	MAX1027_V_CHAN(1),
> +	MAX1027_V_CHAN(2),
> +	MAX1027_V_CHAN(3),
> +	MAX1027_V_CHAN(4),
> +	MAX1027_V_CHAN(5),
> +	MAX1027_V_CHAN(6),
> +	MAX1027_V_CHAN(7),
> +	MAX1027_V_CHAN(8),
> +	MAX1027_V_CHAN(9),
> +	MAX1027_V_CHAN(10),
> +	MAX1027_V_CHAN(11)
> +};
> +
> +static const struct iio_chan_spec max1031_channels[] = {
> +	MAX1027_T_CHAN(0),
> +	MAX1027_V_CHAN(0),
> +	MAX1027_V_CHAN(1),
> +	MAX1027_V_CHAN(2),
> +	MAX1027_V_CHAN(3),
> +	MAX1027_V_CHAN(4),
> +	MAX1027_V_CHAN(5),
> +	MAX1027_V_CHAN(6),
> +	MAX1027_V_CHAN(7),
> +	MAX1027_V_CHAN(8),
> +	MAX1027_V_CHAN(9),
> +	MAX1027_V_CHAN(10),
> +	MAX1027_V_CHAN(11),
> +	MAX1027_V_CHAN(12),
> +	MAX1027_V_CHAN(13),
> +	MAX1027_V_CHAN(14),
> +	MAX1027_V_CHAN(15)
> +};
> +
> +static unsigned long max1027_available_scan_masks[] = {
> +	0x000001ff,
> +	0x00000000,
> +};
> +
> +static unsigned long max1029_available_scan_masks[] = {
> +	0x00001fff,
> +	0x00000000,
> +};
> +
> +static unsigned long max1031_available_scan_masks[] = {
> +	0x0001ffff,
> +	0x00000000,
> +};
> +
> +struct max1027_chip_info {
> +	const struct iio_chan_spec *channels;
> +	unsigned int num_channels;
> +	unsigned long *available_scan_masks;
> +};
> +
> +static const struct max1027_chip_info max1027_chip_info_tbl[] = {
> +	[max1027] = {
> +		.channels = max1027_channels,
> +		.num_channels = ARRAY_SIZE(max1027_channels),
> +		.available_scan_masks = max1027_available_scan_masks,
> +	},
> +	[max1029] = {
> +		.channels = max1029_channels,
> +		.num_channels = ARRAY_SIZE(max1029_channels),
> +		.available_scan_masks = max1029_available_scan_masks,
> +	},
> +	[max1031] = {
> +		.channels = max1031_channels,
> +		.num_channels = ARRAY_SIZE(max1031_channels),
> +		.available_scan_masks = max1031_available_scan_masks,
> +	},
> +};
> +
> +struct max1027_state {
> +	struct max1027_chip_info	*info;
> +	struct spi_device		*spi;
> +	struct iio_trigger		*trig;
> +	u16				*buffer;
> +	struct mutex			lock;
> +};
> +
> +static int max1027_read_single_value(struct iio_dev *indio_dev,
> +				     struct iio_chan_spec const *chan,
> +				     int *val)
> +{
> +	int ret;
> +	unsigned char reg;
> +	struct max1027_state *st = iio_priv(indio_dev);
> +
> +	if (iio_buffer_enabled(indio_dev)) {
> +		dev_warn(&indio_dev->dev, "trigger mode already enabled");
> +		return -EIO;
> +	}
> +
> +	/* Start acquisition on conversion register write */
> +	reg = MAX1027_SETUP_REG | MAX1027_REF_MODE2 | MAX1027_CKS_MODE2;
reg might share a cacheline (see later - note I review backwards as
driver often make more sense that way around!)
> +	ret = spi_write(st->spi, (void *)&reg, 1);
> +	if (ret < 0) {
> +		dev_err(&indio_dev->dev,
> +			"Failed to configure setup register\n");
> +		return ret;
> +	}
> +
> +	/* Configure conversion register with the requested chan */
> +	reg = MAX1027_CONV_REG | MAX1027_CHAN(chan->channel)
> +		| MAX1027_NOSCAN | !!(chan->type == IIO_TEMP);
> +	ret = spi_write(st->spi, (void *)&reg, 1);
> +	if (ret < 0) {
> +		dev_err(&indio_dev->dev,
> +			"Failed to configure conversion register\n");
> +		return ret;
> +	}
> +
> +	/*
> +	 * For an unknown reason, when we use the mode "10" (write
> +	 * conversion register), the it doesn't occur every time.
> +	 * So we just wait 1 ms.
> +	 */
> +	mdelay(1);
> +
> +	/* Read result */
> +	ret = spi_read(st->spi, st->buffer, (chan->type == IIO_TEMP) ? 4 : 2);
> +	if (ret < 0)
> +		return ret;
> +
> +	*val = be16_to_cpu(st->buffer[0]);
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static int max1027_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	int ret = 0;
> +	struct max1027_state *st = iio_priv(indio_dev);
> +
> +	mutex_lock(&st->lock);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = max1027_read_single_value(indio_dev, chan, val);
> +		break;
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->type) {
> +		case IIO_TEMP:
> +			*val = 1;
> +			*val2 = 8;
> +			ret = IIO_VAL_FRACTIONAL;
> +			break;
> +		case IIO_VOLTAGE:
> +			*val = 2500;
> +			*val2 = 10;
> +			ret = IIO_VAL_FRACTIONAL_LOG2;
> +			break;
> +		default:
> +			ret = -EINVAL;
> +			break;
> +		};
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	};
> +
> +	mutex_unlock(&st->lock);
> +
> +	return ret;
> +}
> +
> +static int max1027_debugfs_reg_access(struct iio_dev *indio_dev,
> +				  unsigned reg, unsigned writeval,
> +				  unsigned *readval)
> +{
> +	unsigned char val;
u8 perhaps?
> +	struct max1027_state *st = iio_priv(indio_dev);
> +
> +	if (readval != NULL)
> +		return -EINVAL;
> +
> +	val = (unsigned char)writeval;
Don't think the above cast is needed (though you will need
to copying it as you are doing).

Care needed here - you can't use a buffer on the stack for spi_write
calls as they can be passed straight through for dma and hence need
to be cacheline aligned.  You have a perfectly good buffer in state,
abuse the start of that.
> +	return spi_write(st->spi, (void *)&val, 1);
> +}
> +
> +static int max1027_set_trigger_state(struct iio_trigger *trig, bool state)
> +{
> +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> +	struct max1027_state *st = iio_priv(indio_dev);
Another on stack variable being used for spi writes.  You need to enforce the
alignment or lots of horrible really hard to find bugs will ensue as random
other elements of the cacheline get scrubbed.

> +	unsigned char reg;
> +	int ret;
> +
> +	if (state) {
> +		/* Start acquisition on cnvst */
> +		reg = MAX1027_SETUP_REG | MAX1027_CKS_MODE0 | MAX1027_REF_MODE2;
Clear out all these (void *) casts.  They aren't needed and look
really uggly!  Technically you could spi_write_then_read but not
spi_write.
> +		ret = spi_write(st->spi, (void *)&reg, 1);
> +		if (ret < 0)
> +			return ret;
> +
> +		/* Scan from 0 to max */
> +		reg = MAX1027_CONV_REG | MAX1027_CHAN(0)
> +			| MAX1027_SCAN_N_M | MAX1027_TEMP;
> +		ret = spi_write(st->spi, (void *)&reg, 1);
> +		if (ret < 0)
> +			return ret;
> +	} else {
> +		/* Start acquisition on conversion register write */
> +		reg = MAX1027_SETUP_REG | MAX1027_CKS_MODE2 | MAX1027_REF_MODE2;
> +		ret = spi_write(st->spi, (void *)&reg, 1);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static irqreturn_t max1027_trigger_handler(int irq, void *private)
> +{
> +	struct iio_poll_func *pf = (struct iio_poll_func *)private;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct max1027_state *st = iio_priv(indio_dev);
> +
> +	pr_debug("%s(irq=%d, private=0x%p)\n", __func__, irq, private);
> +
> +	/* fill buffer with all channel */
> +	spi_read(st->spi, st->buffer, indio_dev->masklength * 2);
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, st->buffer,
> +					   iio_get_time_ns());
> +
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static const struct iio_trigger_ops max1027_trigger_ops = {
> +	.owner = THIS_MODULE,
> +	.set_trigger_state = &max1027_set_trigger_state,
> +};
> +
> +static const struct iio_info max1027_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = &max1027_read_raw,
> +	.debugfs_reg_access = &max1027_debugfs_reg_access,
> +};
> +
> +static int max1027_probe(struct spi_device *spi)
> +{
> +	int err;
> +	unsigned char reg;
> +	struct iio_dev *indio_dev;
> +	struct max1027_state *st;
> +
> +	pr_debug("%s: probe(spi = 0x%p)\n", __func__, spi);
> +
> +	/* allocate iio device */
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (indio_dev == NULL) {
> +		pr_err("can't allocate iio device\n");
> +		return -ENOMEM;
> +	}
> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	st = iio_priv(indio_dev);
> +	st->spi = spi;
> +	st->buffer = NULL;
> +	st->info = (struct max1027_chip_info *)
> +		&max1027_chip_info_tbl[spi_get_device_id(spi)->driver_data];
> +
> +	mutex_init(&st->lock);
> +
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->info = &max1027_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = st->info->channels;
> +	indio_dev->num_channels = st->info->num_channels;
> +	indio_dev->available_scan_masks = st->info->available_scan_masks;
> +
> +	/* Allocate buffer (data) */
> +	st->buffer = devm_kmalloc(&indio_dev->dev,
> +				  indio_dev->num_channels * 2,
> +				  GFP_KERNEL);
> +	if (st->buffer == NULL) {
> +		dev_err(&indio_dev->dev, "Can't allocate bufffer\n");
> +		return -ENOMEM;
> +	}
> +
> +	/* Allocate buffer */
> +	err = iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time,
> +					 &max1027_trigger_handler, NULL);
> +	if (err < 0) {
> +		dev_err(&indio_dev->dev, "Failed to setup buffer\n");
> +		return err;
> +	}
> +
> +	/* Allocate trigger */
> +	st->trig = devm_iio_trigger_alloc(&spi->dev, "%s-trigger",
> +							indio_dev->name);
> +	if (st->trig == NULL) {
> +		err = -ENOMEM;
> +		dev_err(&indio_dev->dev, "Failed to allocate iio trigger\n");
> +		goto fail_trigger_alloc;
> +	}
> +
> +	/* configure and register trigger */
> +	st->trig->ops = &max1027_trigger_ops;
> +	st->trig->dev.parent = &spi->dev;
> +	iio_trigger_set_drvdata(st->trig, indio_dev);
> +	iio_trigger_register(st->trig);
> +
> +	/* request irq */
> +	err = devm_request_threaded_irq(&spi->dev, spi->irq,
> +					iio_trigger_generic_data_rdy_poll,
> +					NULL,
> +					IRQF_TRIGGER_FALLING,
> +					spi->dev.driver->name, st->trig);
> +	if (err < 0) {
> +		dev_err(&indio_dev->dev, "Failed to allocate IRQ.\n");
> +		goto fail_dev_register;
> +	}
> +
> +	/* Disable averaging */
> +	reg = MAX1027_AVG_REG;

You shouldn't ever need to cast a function parameter to a void *. Let the
compiler figure out the obvious ;)
> +	err = spi_write(st->spi, (void *)&reg, 1);
> +	if (err < 0) {
> +		dev_err(&indio_dev->dev, "Failed to configure averaging register\n");
> +		goto fail_dev_register;
> +	}
> +
> +	/* Register the device */
> +	err = iio_device_register(indio_dev);
> +	if (err < 0) {
> +		dev_err(&indio_dev->dev, "Failed to register iio device\n");
> +		goto fail_dev_register;
> +	}
> +
> +	return 0;
> +
> +fail_dev_register:
> +fail_trigger_alloc:
> +	iio_triggered_buffer_cleanup(indio_dev);
> +
> +	return err;
> +}
> +
> +static int max1027_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +
> +	pr_debug("%s: remove(spi = 0x%p)\n", __func__, spi);
> +
> +	iio_device_unregister(indio_dev);
> +	iio_triggered_buffer_cleanup(indio_dev);
> +
> +	return 0;
> +}
> +
> +static struct spi_driver max1027_driver = {
> +	.driver = {
> +		.name	= "max1027",
> +		.owner	= THIS_MODULE,
> +	},
> +	.probe		= max1027_probe,
> +	.remove		= max1027_remove,
> +	.id_table	= max1027_id,
> +};
> +module_spi_driver(max1027_driver);
> +
> +MODULE_AUTHOR("Philippe Reynes <tremyfr@...oo.fr>");
> +MODULE_DESCRIPTION("MAX1027/MAX1029/MAX1031 ADC");
> +MODULE_LICENSE("GPL v2");
>

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