Date:   Thu, 15 Apr 2021 11:41:50 +0300
From:   Tomas Melin <tomas.melin@...sala.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     jic23@...nel.org, devicetree@...r.kernel.org,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: accel: Add driver for Murata SCA3300
 accelerometer

On 4/12/21 2:08 PM, Jonathan Cameron wrote:

> On Mon, 12 Apr 2021 10:50:56 +0300
> Tomas Melin <tomas.melin@...sala.com> wrote:
>
>> Add initial support for Murata SCA3300 3-axis industrial
>> accelerometer with digital SPI interface. This device also
>> provides a temperature measurement.
>>
>> Device product page including datasheet can be found at:
>> https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.murata.com%2Fen-global%2Fproducts%2Fsensor%2Faccel%2Fsca3300&amp;data=04%7C01%7Ctomas.melin%40vaisala.com%7Ca66811c95e6c404aa5a208d8fda3743c%7C6d7393e041f54c2e9b124c2be5da5c57%7C0%7C0%7C637538225758011604%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=7bvCd52SFuYdFVlhYrknp0769%2B6hBpxdP6ln0OgKTrE%3D&amp;reserved=0
>>
>> Signed-off-by: Tomas Melin <tomas.melin@...sala.com>
> Hi Tomas,
>
> Comments below.
>
> Thanks,
>
> Jonathan

Hi Jonathan,

Thanks for your comments! I'll get back with a v2.

While working on updates I did notice something new which I cannot

reproduce on older (5.10.17 kernel) version. If compiling this as a 
module, getting error while

unloading module:

[   40.200084] Unable to handle kernel NULL pointer dereference at 
virtual address 00000104
...

[   40.510054] Backtrace:
[   40.512502] [<c06c5e0c>] (iio_device_ioctl_handler_unregister) from 
[<c06ca8c4>] (iio_buffers_free_sysfs_and_mask+0x2c/0x6c)
[   40.523735] [<c06ca898>] (iio_buffers_free_sysfs_and_mask) from 
[<c06c4a18>] (iio_device_unregister+0xa8/0xac)
[   40.533746]  r5:c1811228 r4:c1811000
[   40.537318] [<c06c4970>] (iio_device_unregister) from [<c06c4a38>] 
(devm_iio_device_unreg+0x1c/0x20)
[   40.546461]  r5:c2415000 r4:c25bab80
[   40.550025] [<c06c4a1c>] (devm_iio_device_unreg) from [<c0556820>] 
(release_nodes+0x1c0/0x1f0)
[   40.558654] [<c0556660>] (release_nodes) from [<c0556bb0>] 
(devres_release_all+0x40/0x60)
[   40.566847]  r10:00000081 r9:c2350000 r8:c0100264 r7:00000081 
r6:bf00c010 r5:c19be000
[   40.574669]  r4:c1a91c00
[   40.577194] [<c0556b70>] (devres_release_all) from [<c055216c>] 
(device_release_driver_internal+0x120/0x1cc)
[   40.587031]  r5:c19be000 r4:c1a91c00
[   40.590596] [<c055204c>] (device_release_driver_internal) from 
[<c05522b4>] (driver_detach+0x54/0x90)
[   40.599828]  r7:00000081 r6:00000000 r5:bf00c010 r4:c1a91c00
[   40.605482] [<c0552260>] (driver_detach) from [<c0550ba4>] 
(bus_remove_driver+0x5c/0xb0)
[   40.613583]  r5:00000800 r4:bf00c010
[   40.617148] [<c0550b48>] (bus_remove_driver) from [<c0552c38>] 
(driver_unregister+0x38/0x5c)
[   40.625596]  r5:00000800 r4:bf00c010
[   40.629161] [<c0552c00>] (driver_unregister) from [<bf00a760>] 
(sca3300_driver_exit+0x14/0x8b4 [sca3300])
[   40.638747]  r5:00000800 r4:bf00c080
[   40.642311] [<bf00a74c>] (sca3300_driver_exit [sca3300]) from 
[<c01c06f0>] (sys_delete_module+0x16c/0x238)
[   40.651990] [<c01c0584>] (sys_delete_module) from [<c0100244>] 
(__sys_trace_return+0x0/0x1c)
[   40.660435] Exception stack(0xc2351fa8 to 0xc2351ff0)
[   40.665484] 1fa0:                   0050e5a8 00000000 0050e5e4 
00000800 081d4b00 bec18af4
[   40.673661] 1fc0: 0050e5a8 00000000 bec18b50 00000081 bec18e51 
0050e190 00000001 bec18d3c
[   40.681834] 1fe0: 0050cf70 bec18afc 004f1ec8 b6ecb27c
[   40.686887]  r6:bec18b50 r5:00000000 r4:0050e5a8
[   40.691507] Code: e8bd4000 e1c020d0 e3a0cc01 e3001122 (e5823004)
[   40.707675] ---[ end trace 189882b050077333 ]---

This happens when building against linux-next 5.12.0-rc6-next-20210409. 
I'm failing to see what is wrong. Any ideas?

Thanks,

Tomas


>
>> ---
>>   drivers/iio/accel/Kconfig   |  13 ++
>>   drivers/iio/accel/Makefile  |   1 +
>>   drivers/iio/accel/sca3300.c | 434 ++++++++++++++++++++++++++++++++++++
>>   3 files changed, 448 insertions(+)
>>   create mode 100644 drivers/iio/accel/sca3300.c
>>
>> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
>> index cceda3cecbcf..0dbf7b648e8a 100644
>> --- a/drivers/iio/accel/Kconfig
>> +++ b/drivers/iio/accel/Kconfig
>> @@ -450,6 +450,19 @@ config SCA3000
>>   	  To compile this driver as a module, say M here: the module will be
>>   	  called sca3000.
>>   
>> +config SCA3300
>> +	tristate "Murata SCA3300 3-Axis Accelerometer Driver"
>> +	depends on SPI
>> +	select CRC8
>> +	select IIO_BUFFER
>> +	select IIO_TRIGGERED_BUFFER
>> +	help
>> +	  Say yes here to build support for Murata SCA3300 3-Axis
>> +	  accelerometer.
>> +
>> +	  To compile this driver as a module, choose M here: the module will be
>> +	  called sca3300.
>> +
>>   config STK8312
>>   	tristate "Sensortek STK8312 3-Axis Accelerometer Driver"
>>   	depends on I2C
>> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
>> index 32cd1342a31a..4b56527a2b97 100644
>> --- a/drivers/iio/accel/Makefile
>> +++ b/drivers/iio/accel/Makefile
>> @@ -50,6 +50,7 @@ obj-$(CONFIG_MXC4005)		+= mxc4005.o
>>   obj-$(CONFIG_MXC6255)		+= mxc6255.o
>>   
>>   obj-$(CONFIG_SCA3000)		+= sca3000.o
>> +obj-$(CONFIG_SCA3300)		+= sca3300.o
>>   
>>   obj-$(CONFIG_STK8312)		+= stk8312.o
>>   obj-$(CONFIG_STK8BA50)		+= stk8ba50.o
>> diff --git a/drivers/iio/accel/sca3300.c b/drivers/iio/accel/sca3300.c
>> new file mode 100644
>> index 000000000000..112fb88ecd3a
>> --- /dev/null
>> +++ b/drivers/iio/accel/sca3300.c
>> @@ -0,0 +1,434 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) Vaisala Oyj. All rights reserved.
> Give a year for the copyright notice if you can.
>
>> + */
>> +#include <linux/crc8.h>
>> +#include <linux/delay.h>
>> +#include <linux/iio/buffer.h>
>> +#include <linux/iio/iio.h>
>> +#include <linux/iio/sysfs.h>
>> +#include <linux/iio/trigger_consumer.h>
>> +#include <linux/iio/triggered_buffer.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/spi/spi.h>
>> +
>> +#define SCA3300_ALIAS "sca3300"
>> +
>> +#define SCA3300_REG_STATUS 0x6
>> +#define SCA3300_REG_MODE 0xd
>> +#define SCA3300_REG_WHOAMI 0x10
>> +#define SCA3300_VALUE_SW_RESET 0x20
>> +#define SCA3300_CRC8_POLYNOMIAL 0x1d
>> +#define SCA3300_X_READ 0
> I wouldn't bother defining this.
>
>> +#define SCA3300_X_WRITE BIT(7)
> Even this one is something I'd just put inline with a comment.
>
>> +#define SCA3300_DEVICE_ID 0x51
>> +#define SCA3300_RS_ERROR 0x3
>> +
>> +enum sca3300_scan_indexes {
>> +	SCA3300_ACC_X = 0,
>> +	SCA3300_ACC_Y,
>> +	SCA3300_ACC_Z,
>> +	SCA3300_TEMP,
>> +	SCA3300_TIMESTAMP,
>> +};
>> +
>> +#define SCA3300_ACCEL_CHANNEL(index, reg, axis) {			\
>> +		.type = IIO_ACCEL,					\
>> +		.address = reg,						\
>> +		.modified = 1,						\
>> +		.channel2 = IIO_MOD_##axis,				\
>> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
>> +				      BIT(IIO_CHAN_INFO_PROCESSED),	\
> As mentioned below, don't provide PROCESSED. Userspace is better at handling the
> conversion so leave it to them.
>
>> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
>> +		.scan_index = index,					\
>> +		.scan_type = {						\
>> +			.sign = 's',					\
>> +			.realbits = 16,					\
>> +			.storagebits = 16,				\
>> +			.shift = 0,					\
>> +			.endianness = IIO_CPU,				\
>> +		},							\
>> +	}
>> +
>> +static const struct iio_chan_spec sca3300_channels[] = {
>> +	SCA3300_ACCEL_CHANNEL(SCA3300_ACC_X, 0x1, X),
>> +	SCA3300_ACCEL_CHANNEL(SCA3300_ACC_Y, 0x2, Y),
>> +	SCA3300_ACCEL_CHANNEL(SCA3300_ACC_Z, 0x3, Z),
>> +	{
>> +		.type = IIO_TEMP,
>> +		.address = 0x5,
>> +		.scan_index = SCA3300_TEMP,
>> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
>> +		.scan_type = {
>> +			.sign = 's',
>> +			.realbits = 16,
>> +			.storagebits = 16,
>> +			.shift = 0,
>> +			.endianness = IIO_CPU,
>> +		},
>> +	},
>> +	IIO_CHAN_SOFT_TIMESTAMP(4),
>> +};
>> +
>> +static const int sca3300_accel_scale[] = {2700, 1350, 5400, 5400};
>> +
>> +static const unsigned long sca3300_scan_masks[] = {
>> +	BIT(SCA3300_ACC_X) | BIT(SCA3300_ACC_Y) | BIT(SCA3300_ACC_Z) |
>> +	BIT(SCA3300_TEMP),
>> +	0};
>> +
>> +/**
>> + * SCA3300 device data
> run scripts/kernel-doc over the file and fix the warnings + errors.
>
>> + *
>> + * @spi SPI device structure
>> + * @opmode Device operation mode
>> + * @lock Data buffer lock
>> + * @txbuf Transmit buffer
>> + * @rxbuf Receive buffer
>> + * @scan Triggered buffer. Four channel 16-bit data + 64-bit timestamp
>> + */
>> +struct sca3300_data {
>> +	struct spi_device *spi;
>> +	u32 opmode;
>> +	struct mutex lock;
>> +	u8 txbuf[4];
>> +	u8 rxbuf[4];
>> +	struct {
>> +		s16 channels[4];
>> +		s64 ts __aligned(sizeof(s64));
>> +	} scan;
>> +};
>> +
>> +DECLARE_CRC8_TABLE(sca3300_crc_table);
>> +
>> +static int sca3300_transfer(struct sca3300_data *sca_data, int *val)
>> +{
>> +	struct spi_delay delay = {.value = 10, .unit = SPI_DELAY_UNIT_USECS};
>> +	int32_t ret;
>> +	int rs;
>> +	u8 crc;
>> +	struct spi_transfer xfers[2] = {
>> +		{
>> +			.tx_buf = sca_data->txbuf,
>> +			.rx_buf = NULL,
>> +			.len = ARRAY_SIZE(sca_data->txbuf),
>> +			.delay = delay,
>> +			.cs_change = 1,
>> +		},
>> +		{
>> +			.tx_buf = NULL,
>> +			.rx_buf = sca_data->rxbuf,
>> +			.len = ARRAY_SIZE(sca_data->rxbuf),
>> +			.delay = delay,
>> +			.cs_change = 0,
>> +		}
>> +	};
>> +
>> +	/* inverted crc value as described in device data sheet */
>> +	crc = ~crc8(sca3300_crc_table, &sca_data->txbuf[0], 3, CRC8_INIT_VALUE);
>> +	sca_data->txbuf[3] = crc;
>> +
>> +	ret = spi_sync_transfer(sca_data->spi, xfers, 2);
> Use ARRAY_SIZE(xfers) instead of 2.
>
>> +	if (ret < 0) {
>> +		dev_err(&sca_data->spi->dev,
>> +			"transfer error, error: %d\n", ret);
>> +		return -EIO;
>> +	}
>> +
>> +	crc = ~crc8(sca3300_crc_table, &sca_data->rxbuf[0], 3, CRC8_INIT_VALUE);
>> +	if (sca_data->rxbuf[3] != crc) {
>> +		dev_err(&sca_data->spi->dev, "CRC checksum mismatch");
>> +		return -EIO;
>> +	}
>> +
>> +	/* get return status */
>> +	rs = sca_data->rxbuf[0] & 0x03;
>> +	if (rs == SCA3300_RS_ERROR)
>> +		return rs;
>> +
>> +	*val = (s16)(sca_data->rxbuf[2] | (sca_data->rxbuf[1] << 8));
> Preference for an unaligned endian conversion here and explicit sign extend e.g
> something like
>
> sign_extend32(get_unaligned_le16(&sca_data->rxbuf[1]), 15)
>
>> +
>> +	return 0;
>> +}
>> +
>> +static int sca3300_read_reg(struct sca3300_data *sca_data, u8 reg, int *val)
>> +{
>> +	int ret;
>> +
>> +	mutex_lock(&sca_data->lock);
>> +	sca_data->txbuf[0] = SCA3300_X_READ | (reg << 2);
>> +	ret = sca3300_transfer(sca_data, val);
>> +	if (ret > 0) {
>> +		sca_data->txbuf[0] = SCA3300_X_READ | (SCA3300_REG_STATUS << 2);
>> +		ret = sca3300_transfer(sca_data, val);
>> +		/* status 0 = startup, 0x2 = mode change */
>> +		if (ret > 0 && *val != 0 && *val != 0x2) {
>> +			dev_err_ratelimited(&sca_data->spi->dev,
>> +					    "device status: %x\n",
>> +					    (u16)*val);
>> +			mutex_unlock(&sca_data->lock);
>> +			return -EIO;
>> +		}
>> +		if (ret > 0)
>> +			ret = 0;
>> +	}
>> +	mutex_unlock(&sca_data->lock);
>> +
>> +	return ret;
>> +}
>> +
>> +static int sca3300_write_reg(struct sca3300_data *sca_data, u8 reg, int val)
>> +{
>> +	int reg_val = 0;
>> +	int ret;
>> +
>> +	mutex_lock(&sca_data->lock);
>> +	sca_data->txbuf[0] = SCA3300_X_WRITE | (reg << 2);
>> +	sca_data->txbuf[1] = val >> 8;
>> +	sca_data->txbuf[2] = val & 0xFF;
> Prefer (Slightly) an unaligned put.
>
>> +	ret = sca3300_transfer(sca_data, &reg_val);
>> +	if (ret > 0) {
> Factor this error handling out to another function, plus trigger it from an
> appropriate standard error code rather than a positive return value.
>
>> +		sca_data->txbuf[0] = SCA3300_X_READ | (SCA3300_REG_STATUS << 2);
>> +		ret = sca3300_transfer(sca_data, &reg_val);
>> +		/* status 0 = startup, 0x2 = mode change */
>> +		if (ret > 0 && reg_val != 0 && reg_val != 0x2) {
>> +			dev_err_ratelimited(&sca_data->spi->dev,
>> +					    "device status: %x\n",
>> +					    (u16)reg_val);
>> +			mutex_unlock(&sca_data->lock);
>> +			return -EIO;
>> +		}
>> +		if (ret > 0)
>> +			ret = 0;
> Whenever you get this sort of juggling it rather implies your design is
> less than ideal.
>
>> +	}
>> +	mutex_unlock(&sca_data->lock);
>> +
>> +	return ret;
>> +}
>> +
>> +static int sca3300_write_raw(struct iio_dev *indio_dev,
>> +			     struct iio_chan_spec const *chan,
>> +			     int val, int val2, long mask)
>> +{
>> +	struct sca3300_data *data = iio_priv(indio_dev);
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_SCALE:
>> +		if (val < 0 || val > 3)
>> +			return -EINVAL;
> No.  Scale values need to be the value of 1LSB not a random integer
> that requires you to look up the datasheet.
>
>> +		return sca3300_write_reg(data, SCA3300_REG_MODE, val);
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +}
>> +
>> +static int sca3300_read_raw(struct iio_dev *indio_dev,
>> +			    struct iio_chan_spec const *chan,
>> +			    int *val, int *val2, long mask)
>> +{
>> +	struct sca3300_data *data = iio_priv(indio_dev);
>> +	int ret;
>> +	int reg_val;
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		ret = sca3300_read_reg(data, chan->address, val);
>> +		if (ret < 0)
>> +			return ret;
>> +		return IIO_VAL_INT;
>> +	case IIO_CHAN_INFO_SCALE:
>> +		ret = sca3300_read_reg(data, SCA3300_REG_MODE, &reg_val);
>> +		if (ret < 0)
>> +			return ret;
>> +		*val = sca3300_accel_scale[reg_val];
> Scale is very very rarely an integer value which makes me wonder what
> you are returning here...  It should be the multiplier needed to
> take the raw value to a reading in m/sec^2  Given you use it as fractional
> below, I'm guessing this is 1/scale_value?
>
>> +		return IIO_VAL_INT;
>> +	case IIO_CHAN_INFO_PROCESSED:
> Don't provide processed here.   Userspace needs to do the conversion itself
> (and given it has floating point easily available will probably do a better
>   job than we can).   I'm assuming the mode can't autonomously change?
>
>> +		ret = sca3300_read_reg(data, SCA3300_REG_MODE, &reg_val);
>> +		if (ret < 0)
>> +			return ret;
>> +		*val2 = sca3300_accel_scale[reg_val];
>> +		ret = sca3300_read_reg(data, chan->address, val);
>> +		if (ret < 0)
>> +			return ret;
>> +		return IIO_VAL_FRACTIONAL;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +}
>> +
>> +static irqreturn_t sca3300_trigger_handler(int irq, void *p)
>> +{
>> +	struct iio_poll_func *pf = p;
>> +	struct iio_dev *indio_dev = pf->indio_dev;
>> +	struct sca3300_data *data = iio_priv(indio_dev);
>> +	s64 time_ns = iio_get_time_ns(indio_dev);
> Is the timestamp at the start more accurate that that at the end
> of reading the channels?  If not, just put this inline in the
> iio_push_to_buffers_with_timestamp() call.
>
>> +	int bit, ret, val, i = 0;
>> +
>> +	for_each_set_bit(bit, indio_dev->active_scan_mask,
>> +			 indio_dev->masklength) {
>> +		ret = sca3300_read_reg(data, sca3300_channels[bit].address,
>> +				       &val);
>> +		if (ret < 0)
> Given we can't return an error code from interrupt handlers, it is usually
> a good idea to print something to the log. Otherwise we get missing data
> with no idea of why..
>
>> +			goto out;
>> +		if (ARRAY_SIZE(data->scan.channels) > i)
> How could this not be true?  If it's always true, don't bother
> checking i.
>
>> +			((s16 *)data->scan.channels)[i++] = val;
>> +	}
>> +
>> +	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan, time_ns);
>> +out:
>> +	iio_trigger_notify_done(indio_dev->trig);
>> +
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static int sca3300_init(struct sca3300_data *sca_data,
>> +			struct iio_dev *indio_dev)
>> +{
>> +	int ret;
>> +	int value = 0;
>> +
>> +	if (sca_data->opmode < 1 || sca_data->opmode > 4)
>> +		return -EINVAL;
> Whilst this is going anyway, better to check that next to where
> it is read so we drop out immediately rather than buried in this
> function.
>
>> +
>> +	ret = sca3300_write_reg(sca_data, SCA3300_REG_MODE,
>> +				SCA3300_VALUE_SW_RESET);
>> +	if (ret != 0)
>> +		return ret;
> For sleeps, good to reference which section in data sheet gives the
> timing.
>
>> +	usleep_range(2e3, 10e3);
>> +
>> +	ret = sca3300_write_reg(sca_data, SCA3300_REG_MODE,
>> +				sca_data->opmode - 1);
>> +	if (ret != 0)
> if (ret) see below.
>
>> +		return ret;
>> +	msleep(100);
> Again, document where the time comes from. Saves reviewers time if
> they want to check it. (I'm too lazy :)
>
>> +	ret = sca3300_read_reg(sca_data, SCA3300_REG_WHOAMI, &value);
>> +	if (ret != 0)
> if (ret) is more idiomatic in kernel code.
>
>> +		return ret;
>> +
>> +	if (value != SCA3300_DEVICE_ID) {
>> +		dev_err(&sca_data->spi->dev, "device id not expected value\n");
> Perhaps useful to print what was expected and what was seen.  Maybe it's
> a new variant and this might help the user to identify that and add it to the
> driver.
>
>> +		return -EIO;
> -EINVAL probably more appropriate return.
>
>> +	}
>> +	return 0;
>> +}
>> +
>> +static int sca3300_debugfs_reg_access(struct iio_dev *indio_dev,
>> +				      unsigned int reg, unsigned int writeval,
>> +				      unsigned int *readval)
>> +{
>> +	struct sca3300_data *data = iio_priv(indio_dev);
>> +	int value;
>> +	int ret;
>> +
>> +	if (reg > 0x1f)
> Use a define that names that register.
>
>> +		return -EINVAL;
>> +
>> +	if (!readval)
>> +		return sca3300_write_reg(data, reg, writeval);
>> +
>> +	ret = sca3300_read_reg(data, reg, &value);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	*readval = (unsigned int)value;
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct iio_info sca3300_info = {
>> +	.read_raw = sca3300_read_raw,
>> +	.write_raw = sca3300_write_raw,
>> +	.debugfs_reg_access = &sca3300_debugfs_reg_access,
>> +};
>> +
>> +static int sca3300_probe(struct spi_device *spi)
>> +{
>> +	struct sca3300_data *sca_data;
>> +	struct iio_dev *indio_dev;
>> +	int ret;
>> +
>> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*sca_data));
>> +	if (!indio_dev) {
>> +		dev_err(&spi->dev,
>> +			"failed to allocate memory for iio device\n");
>> +		return -ENOMEM;
>> +	}
>> +
>> +	sca_data = iio_priv(indio_dev);
>> +	mutex_init(&sca_data->lock);
>> +	sca_data->spi = spi;
>> +	spi_set_drvdata(spi, indio_dev);
> Won't be used once using devm as below and remove() is dropped, so drop this.
>
>> +
>> +	crc8_populate_msb(sca3300_crc_table, SCA3300_CRC8_POLYNOMIAL);
>> +
>> +	indio_dev->dev.parent = &spi->dev;
>> +	indio_dev->info = &sca3300_info;
>> +	indio_dev->name = SCA3300_ALIAS;
>> +	indio_dev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_TRIGGERED;
> BUFFER_TRIGGERED bit now set by iio_triggered_buffer_setup() so shouldn't
> be ehre as well.
>
>> +	indio_dev->channels = sca3300_channels;
>> +	indio_dev->num_channels = ARRAY_SIZE(sca3300_channels);
>> +	indio_dev->available_scan_masks = sca3300_scan_masks;
>> +
>> +	if (spi->dev.of_node) {
>> +		ret = of_property_read_u32(spi->dev.of_node, "murata,opmode",
> Please use generic firmware access calls rather than the of specific ones.
> That lets us get ACPI support for free :)
>
> As per the binding review however, this one needs to go in favour of userspace
> control of scale + filter frequencies / sampling freq.
>
>> +					   &sca_data->opmode);
>> +		if (ret < 0)
>> +			return ret;
>> +	}
>> +
>> +	ret = sca3300_init(sca_data, indio_dev);
>> +	if (ret < 0) {
>> +		dev_err(&spi->dev, "failed to init device, error: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time,
>> +					 sca3300_trigger_handler, NULL);
> devm_iio_triggered_buffer_setup() and you can drop the manual cleanup in remove()
> and hence drop remove() entirely as nothing else left.
>
>> +	if (ret < 0) {
>> +		dev_err(&spi->dev,
>> +			"iio triggered buffer setup failed, error: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	ret = devm_iio_device_register(&spi->dev, indio_dev);
>> +	if (ret < 0) {
>> +		dev_err(&spi->dev, "iio device register failed, error: %d\n",
>> +			ret);
>> +		iio_triggered_buffer_cleanup(indio_dev);
> With devm above, no need to manually clean this up.
>
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int sca3300_remove(struct spi_device *spi)
>> +{
>> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
>> +
>> +	iio_triggered_buffer_cleanup(indio_dev);
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id sca3300_dt_ids[] = {
>> +	{ .compatible = "murata,sca3300"},
>> +	{},
>> +};
>> +MODULE_DEVICE_TABLE(of, sca3300_dt_ids);
>> +
>> +static struct spi_driver sca3300_driver = {
>> +	.driver = {
>> +		.name		= SCA3300_ALIAS,
>> +		.owner		= THIS_MODULE,
>> +		.of_match_table = of_match_ptr(sca3300_dt_ids),
>> +	},
>> +
>> +	.probe	= sca3300_probe,
>> +	.remove	= sca3300_remove,
>> +};
>> +
>> +module_spi_driver(sca3300_driver);
>> +
>> +MODULE_AUTHOR("Tomas Melin <tomas.melin@...sala.com>");
>> +MODULE_DESCRIPTION("Murata SCA3300 SPI Accelerometer");
>> +MODULE_LICENSE("GPL v2");

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