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Date: Sat, 14 Jun 2014 15:42:09 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Hartmut Knaack <knaack.h@....de>,
Philippe Reynes <tremyfr@...oo.fr>, linux-iio@...r.kernel.org
CC: linux-kernel@...r.kernel.org, armadeus-forum@...ts.sourceforge.net,
lars@...afoo.de, devicetree@...r.kernel.org, pmeerw@...erw.net
Subject: Re: [PATCH v6] iio: add support of the max1027
On 14/06/14 15:09, Jonathan Cameron wrote:
> On 14/06/14 14:52, Hartmut Knaack wrote:
>> Philippe Reynes schrieb:
>>> 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,
>
> There's just enough stuff in here in my review that I'd rather you rolled
> a V7 rather than me just fixing it up during the apply.
>
> Last time round ;)
>
> Jonathan
>>> ---
>>> .../devicetree/bindings/iio/adc/max1027-adc.txt | 22 +
>>> drivers/iio/adc/Kconfig | 9 +
>>> drivers/iio/adc/Makefile | 1 +
>>> drivers/iio/adc/max1027.c | 522 ++++++++++++++++++++
>>> 4 files changed, 554 insertions(+), 0 deletions(-)
>>> create mode 100644 Documentation/devicetree/bindings/iio/adc/max1027-adc.txt
>>> create mode 100644 drivers/iio/adc/max1027.c
>>>
>>> Changelog:
>>> v6: (thanks Peter Meerwald for the feedback)
>>> - dont use index with temperature
>>> - use const on scan mask
>>> - use __be16 * for buffer
>>> - return -EBUSY if trigger is already running
>>> - replace it by interrupt in comment
>>> - dont finish case with ";"
>>> - use iio_push_to_buffers
>>> - remove useless initialization of st->buffer
>>> - remove useless obvious comment
>>>
>>> v5: (thanks Jonathan Cameron for the feedback)
>>> - add validate_trigger
>>> - add validate_device
>>> - remove useless (void *) cast
>>> - use allocated buffer for spi_write
>>>
>>> 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..92d6c7f
>>> --- /dev/null
>>> +++ b/drivers/iio/adc/max1027.c
>>> @@ -0,0 +1,522 @@
>>> + /*
>>> + * 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>
>>> +
>> We had some tendency on the list lately to include bitops.h and use
>> BIT(n) instead of 1 << n. Jonathan, is it "planned" to switch to that
>> style for the whole IIO subsystem? If so, it would safe some cleanup
>> to implement it already in new drivers.
> This definitely comes in the category of things I really find it hard
> to care about either way.
> So nope, not going to suggest we tidy this up in new drivers (or indeed
> in the subsystem). If people feel it makes some element of code easier to
> read then fair enough.
Having said this, I just reached Peter's patches. It is definitely worth
bitops conversion if there are any masks about. I'm still not going to
argue that any given driver should do it, but Peter has cleared out some
local rewrites of the GENMASK macro and that was worthwhile!
>
>>> +#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, \
>> Separate operators with whitespaces.
>>> + .scan_type = { \
>>> + .sign = 'u', \
>>> + .realbits = 10, \
>>> + .storagebits = 16, \
>>> + .shift = 2, \
>>> + .endianness = IIO_BE, \
>>> + }, \
>>> + }
>>> +
>>> +#define MAX1027_T_CHAN \
>>> + { \
>>> + .type = IIO_TEMP, \
>>> + .channel = 0, \
>>> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
>>> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
>>> + .scan_index = 0, \
>>> + .scan_type = { \
>>> + .sign = 'u', \
>>> + .realbits = 12, \
>>> + .storagebits = 16, \
>>> + .endianness = IIO_BE, \
>>> + }, \
>>> + }
>>> +
>>> +static const struct iio_chan_spec max1027_channels[] = {
>>> + MAX1027_T_CHAN,
>>> + 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,
>>> + 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,
>>> + 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 const unsigned long max1027_available_scan_masks[] = {
>>> + 0x000001ff,
>>> + 0x00000000,
>>> +};
>>> +
>>> +static const unsigned long max1029_available_scan_masks[] = {
>>> + 0x00001fff,
>>> + 0x00000000,
>>> +};
>>> +
>>> +static const unsigned long max1031_available_scan_masks[] = {
>>> + 0x0001ffff,
>>> + 0x00000000,
>>> +};
>>> +
>>> +struct max1027_chip_info {
>>> + const struct iio_chan_spec *channels;
>>> + unsigned int num_channels;
>>> + const 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;
>>> + __be16 *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;
>>> + struct max1027_state *st = iio_priv(indio_dev);
>>> + unsigned char *reg = (unsigned char *)st->buffer;
>>> +
>>> + if (iio_buffer_enabled(indio_dev)) {
>>> + dev_warn(&indio_dev->dev, "trigger mode already enabled");
>>> + return -EBUSY;
>>> + }
>>> +
>>> + /* Start acquisition on conversion register write */
>>> + *reg = MAX1027_SETUP_REG | MAX1027_REF_MODE2 | MAX1027_CKS_MODE2;
>>> + ret = spi_write(st->spi, 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, 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 interrupt 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)
>>> +{
>>> + struct max1027_state *st = iio_priv(indio_dev);
>>> + unsigned char *val = (unsigned char *)st->buffer;
>>> +
>>> + if (readval != NULL)
>>> + return -EINVAL;
>>> +
>>> + *val = (unsigned char)writeval;
>>> + return spi_write(st->spi, val, 1);
>>> +}
>>> +
>>> +static int max1027_validate_trigger(struct iio_dev *indio_dev,
>>> + struct iio_trigger *trig)
>>> +{
>>> + struct max1027_state *st = iio_priv(indio_dev);
>>> +
>>> + if (st->trig != trig)
>>> + return -EINVAL;
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +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 = (unsigned char *)st->buffer;
>>> + int ret;
>>> +
>>> + if (state) {
>>> + /* Start acquisition on cnvst */
>>> + *reg = MAX1027_SETUP_REG|MAX1027_CKS_MODE0|MAX1027_REF_MODE2;
>> Also put some a whitespace around operators here.
>>> + ret = spi_write(st->spi, 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, reg, 1);
>>> + if (ret < 0)
>>> + return ret;
>>> + } else {
>>> + /* Start acquisition on conversion register write */
>>> + *reg = MAX1027_SETUP_REG|MAX1027_CKS_MODE2|MAX1027_REF_MODE2;
>> And here as well.
>>> + ret = spi_write(st->spi, reg, 1);
>>> + if (ret < 0)
>>> + return ret;
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static int max1027_validate_device(struct iio_trigger *trig,
>>> + struct iio_dev *indio_dev)
>>> +{
>>> + struct iio_dev *indio = iio_trigger_get_drvdata(trig);
>>> +
>>> + if (indio != indio_dev)
>>> + return -EINVAL;
>>> +
>>> + 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(indio_dev, st->buffer);
>>> +
>>> + iio_trigger_notify_done(indio_dev->trig);
>>> +
>>> + return IRQ_HANDLED;
>>> +}
>>> +
>>> +static const struct iio_trigger_ops max1027_trigger_ops = {
>>> + .owner = THIS_MODULE,
>>> + .validate_device = &max1027_validate_device,
>>> + .set_trigger_state = &max1027_set_trigger_state,
>>> +};
>>> +
>>> +static const struct iio_info max1027_info = {
>>> + .driver_module = THIS_MODULE,
>>> + .read_raw = &max1027_read_raw,
>>> + .validate_trigger = &max1027_validate_trigger,
>>> + .debugfs_reg_access = &max1027_debugfs_reg_access,
>>> +};
>>> +
>>> +static int max1027_probe(struct spi_device *spi)
>>> +{
>>> + int err;
>> After calling your error/return value ret before, it would be more consistent to do the same here.
>>> + unsigned char *reg;
>>> + struct iio_dev *indio_dev;
>>> + struct max1027_state *st;
>>> +
>>> + pr_debug("%s: probe(spi = 0x%p)\n", __func__, spi);
>>> +
>>> + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
>>> + if (indio_dev == NULL) {
>>> + pr_err("can't allocate iio device\n");
>> Start sentence with capital letter.
>>> + return -ENOMEM;
>>> + }
>>> +
>>> + spi_set_drvdata(spi, indio_dev);
>>> +
>>> + st = iio_priv(indio_dev);
>>> + st->spi = spi;
>>> + 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;
>>> +
>>> + 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;
>>> + }
>>> +
>>> + 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;
>>> + }
>>> +
>>> + 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;
>>> + }
>>> +
>>> + 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);
>>> +
>>> + 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 = (unsigned char *)st->buffer;
>>> + *reg = MAX1027_AVG_REG;
>> What is your intention here? Why not define reg independently as u8 (or unsigned char, if it really has to be) and set your desired value?
> This will be avoiding cacheline issues for the spi_write and trying to avoid allocating two cachelines
> just to have 1 spare bytes to play with.
>
> This could be handled by an annonymous union, but they tend to just make code harder to read.
> (I typed a suggestion to do this in my review then deleted it as probably being a bad idea ;)
>>> + err = spi_write(st->spi, reg, 1);
>>> + if (err < 0) {
>>> + dev_err(&indio_dev->dev, "Failed to configure averaging register\n");
>>> + goto fail_dev_register;
>>> + }
>>> +
>>> + 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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>
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