Date:	Sat, 24 May 2014 12:29:34 +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
Subject: Re: [PATCH v2] iio: add support of the max1027

On 20/05/14 22:27, 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>
> ---
>   .../devicetree/bindings/iio/adc/max1027-adc.txt    |   21 +
>   drivers/staging/iio/adc/Kconfig                    |    9 +
>   drivers/staging/iio/adc/Makefile                   |    1 +
>   drivers/staging/iio/adc/max1027.c                  |  553 ++++++++++++++++++++
>   4 files changed, 584 insertions(+), 0 deletions(-)
>   create mode 100644 Documentation/devicetree/bindings/iio/adc/max1027-adc.txt
>   create mode 100644 drivers/staging/iio/adc/max1027.c
>
> Changelog:
> 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)
Much improved.   A few more bits and pieces inline.  Also the bindings doc
needs a bit of tidying up.  Note that we'll either need an ack from a device
tree maintainer or to wait for 3+ weeks after anyone who has commented is
happy.  That will mean this is unlikely to make the next merge window I'm
afraid.

Anyhow in summary:
1) Drop the empty update_scan_mode callback.
2) Locking needed in the single channel reading code (maybe elsewhere?)
3) Get rid of the wrappers around the spi_read and spi_write.  They add
    code but no real advantages over directly calling the spi_read/write
    instead.
4) Check the available can masks - I think you've missed one bit because
    we have a temperature channel as well as the adc channels.
5) Check the headers you have included and remove any that aren't actually
    necessary.

So other than the device tree binding review, not more than 10 mins work
to my eyes!

Looking forward to the next version.

Jonathan
>
> 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..2e8b9f3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/max1027-adc.txt
> @@ -0,0 +1,21 @@
> +* Maxim 1027/1029/1031 Analog to Digital Converter (ADC)
> +
> +Required properties:
> +  - compatible: Should be "maxim,max1027" or "maxim,max1029" or "maxim,max1031"
> +  - reg: Should contain the ADC SPI address
I'm lost - what's an SPI address?
> +  - interrupt-parent: the phandle for the gpio controller
> +  - interrupts: (gpio) interrupt to which the chip is connected
Doesn't need to be a gpio that I can see so don't specify that.
Also, I believe the general convention is to just reference the interrupts
device tree docs rather than attempting to repeat the information here.
> +
> +Example:
> +adc@0 {
> +	compatible = "maxim,max1027";
> +	reg = <0>;
> +	interrupt-parent = <&gpio5>;
> +	interrupts = <15 IRQ_TYPE_EDGE_RISING>;
> +	pinctrl-names = "default";
> +	pinctrl-0 = <&pinctrl_max1027>;
I'd have a simpler example without the pinctrl stuff.
  
> +	/* SPI mode = 0 */
> +	spi-cpol = <0>;
> +	spi-cpha = <0>;
> +	spi-max-frequency = <1000000>;
Should probably reference the spi docs in the description above for this
bit.
> +};
> diff --git a/drivers/staging/iio/adc/Kconfig b/drivers/staging/iio/adc/Kconfig
> index 3633298..12a78eb 100644
> --- a/drivers/staging/iio/adc/Kconfig
> +++ b/drivers/staging/iio/adc/Kconfig
> @@ -112,6 +112,15 @@ config LPC32XX_ADC
>   	  activate only one via device tree selection.  Provides direct access
>   	  via sysfs.
>
> +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 MXS_LRADC
>   	tristate "Freescale i.MX23/i.MX28 LRADC"
>   	depends on ARCH_MXS || COMPILE_TEST
> diff --git a/drivers/staging/iio/adc/Makefile b/drivers/staging/iio/adc/Makefile
> index 3e9fb14..22fbd0c 100644
> --- a/drivers/staging/iio/adc/Makefile
> +++ b/drivers/staging/iio/adc/Makefile> @@ -18,5 +18,6 @@ obj-$(CONFIG_AD7816) += ad7816.o
>   obj-$(CONFIG_AD7192) += ad7192.o
>   obj-$(CONFIG_AD7280) += ad7280a.o
>   obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
> +obj-$(CONFIG_MAX1027) += max1027.o
>   obj-$(CONFIG_MXS_LRADC) += mxs-lradc.o
>   obj-$(CONFIG_SPEAR_ADC) += spear_adc.o
> diff --git a/drivers/staging/iio/adc/max1027.c b/drivers/staging/iio/adc/max1027.c
> new file mode 100644
> index 0000000..c2e5936
> --- /dev/null
> +++ b/drivers/staging/iio/adc/max1027.c
> @@ -0,0 +1,553 @@
> + /*
> +  * 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/spi/spi.h>
> +#include <linux/module.h>
> +#include <linux/interrupt.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/of_gpio.h>
Why include of_gpio.h?

> +#include <linux/platform_device.h>
It's not a platform device so why is this here?

> +#include <linux/delay.h>
> +#include <linux/gpio.h>
Why include gpio.h?

Check all your included headers for relevance please.
> +
> +#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_12   (0x02 << 2)
> +#define MAX1027_NAVG_16   (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),	\
> +		.address = index,					\
Is address used anywhere?  If not don't bother filling it in.
> +		.scan_index = index+1,					\
spacing around the + please.  Run checkpatch.pl over the patch and it'll
probably catch this sort of trivial thing.
> +		.scan_type = {						\
> +			.sign = 'u',					\
> +			.realbits = 10,					\
> +			.storagebits = 16,				\
> +			.shift = 2,					\
> +			.endianness = IIO_BE,				\
> +		},							\
> +	}
> +
> +#define MAX1027_T_CHAN(index)						\
> +	{								\
> +		.type = IIO_TEMP,					\
> +		.indexed = 0,						\
No need to specify the = 0 as the at is the default...
> +		.channel = index,					\
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +		.address = index,					\
> +		.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[] = {
> +	0x00ff,
I don't think this is correct as it ignores the temperature
channel (or technically the last adc channel - but I guess
you ended up with this by forgetting the temperature channel)
Probably should be 0x01ff,
> +	0x0000,
> +};
> +
> +static unsigned long max1029_available_scan_masks[] = {
> +	0x0fff,
0x1fff,
> +	0x0000,
> +};
> +
> +static unsigned long max1031_available_scan_masks[] = {
> +	0xffff,
0x1ffff,
> +	0x0000,
> +};
> +
> +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;
> +	unsigned short			*buffer;
> +};
> +
> +static int max1027_write_register(struct max1027_state *st, unsigned char reg)
> +{
> +	int ret;
> +
> +	pr_debug("%s(st = 0x%p, reg = 0x%02x)\n", __func__, st, reg);
> +
> +	ret = spi_write(st->spi, (void *)&reg, 1);
> +	if (ret < 0)
> +		pr_err("can't write register\n");
> +
> +	return ret;
> +}
> +
> +static int max1027_read_value(struct max1027_state *st, int len)
> +{
> +	int ret;
> +

I'd drop the debug as it doesn't add all that much.  Then this
wrapper becomes trivial so drop the whole thing (same with the write
above).  Call the spi_read / spi_write directly where needed.

That way we get a marginally shorter and easier to review driver...

> +	pr_debug("%s(st = 0x%p, len = %d)\n", __func__, st, len);
> +
> +	ret = spi_read(st->spi, st->buffer, len);
> +	if (ret < 0)
> +		pr_err("can't read value\n");
> +
> +	return ret;
> +}
> +

This needs locking.  Technically there is nothing preventing two reads
being in flight at the same time.  Obviously you could take a lock
before calling this function, but either way one is needed around
the write then read pair.
> +static int max1027_read_single_value(struct iio_dev *indio_dev,
> +				     struct iio_chan_spec const *chan,
> +				     int *val, int *val2, long mask)
> +{
> +	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;
> +	ret = max1027_write_register(st, reg);
> +	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 = max1027_write_register(st, reg);
> +	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 = max1027_read_value(st, (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;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = max1027_read_single_value(indio_dev, chan,
> +						val, val2, mask);
> +		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;
> +	};
> +
> +	return ret;
> +}
> +
Please don't create callbacks just for the sake of it.
This function does nothing (as the scan mode cannot be changed)
so get rid of it.
> +static int max1027_update_scan_mode(struct iio_dev *indio_dev,
> +				    const unsigned long *scan_mask)
> +{
> +	pr_debug("%s(indio_dev=0x%p, scan_mask=0x%p)\n",
> +		__func__, indio_dev, scan_mask);
> +
> +	return 0;
> +}
> +
> +static int max1027_debugfs_reg_access(struct iio_dev *indio_dev,
> +				  unsigned reg, unsigned writeval,
> +				  unsigned *readval)
> +{
> +	struct max1027_state *st = iio_priv(indio_dev);
> +
> +	if (readval != NULL)
> +		return -EINVAL;
> +
> +	return max1027_write_register(st, writeval);
> +}
> +
> +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);
> +	unsigned char reg;
> +	int ret;
> +
> +	if (state) {
> +		/* Start acquisition on cnvst */
> +		reg = MAX1027_SETUP_REG | MAX1027_CKS_MODE0 | MAX1027_REF_MODE2;
> +		ret = max1027_write_register(st, reg);
> +		if (ret < 0)
> +			return ret;
> +
> +		/* Scan from 0 to max */
> +		reg = MAX1027_CONV_REG | MAX1027_CHAN(0)
> +			| MAX1027_SCAN_N_M | MAX1027_TEMP;
> +		ret = max1027_write_register(st, reg);
> +		if (ret < 0)
> +			return ret;
> +	} else {
> +		/* Start acquisition on conversion register write */
> +		reg = MAX1027_SETUP_REG | MAX1027_REF_MODE2 | MAX1027_CKS_MODE2;
> +		ret = max1027_write_register(st, reg);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static irqreturn_t max1027_interrupt_handler(int irq, void *private)
> +{
> +	struct iio_dev *indio_dev = (struct iio_dev *)private;
> +
> +	pr_debug("%s(irq=%d, private=0x%p)\n", __func__, irq, private);
> +
> +	if (iio_buffer_enabled(indio_dev))
> +		iio_trigger_poll(indio_dev->trig, iio_get_time_ns());
> +
> +	return IRQ_HANDLED;
> +}
> +
> +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 */
> +	max1027_read_value(st, 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,
> +	.update_scan_mode = &max1027_update_scan_mode,
> +	.debugfs_reg_access = &max1027_debugfs_reg_access,
> +};
> +
> +static int max1027_probe(struct spi_device *spi)
> +{
> +	int err;
> +	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(struct max1027_state));
Slight preference for sizeof(*st)) as it makes everything a tiny
bit more obvious to my mind..
> +	if (!indio_dev) {
> +		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];
> +
> +	/* request irq */
> +	err = devm_request_threaded_irq(&spi->dev, spi->irq,
> +					max1027_interrupt_handler,
> +					NULL,
> +					IRQF_TRIGGER_FALLING,
> +					spi->dev.driver->name, indio_dev);
> +	if (err) {
> +		dev_err(&indio_dev->dev, "Failed to allocate IRQ.\n");
> +		return err;
> +	}
> +
> +	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);
> +
> +	/* Disable averaging */
> +	err = max1027_write_register(st, MAX1027_AVG_REG);
> +	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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