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Date:   Mon, 19 Apr 2021 20:45:08 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Tomas Melin <tomas.melin@vaisala.com>
Cc:     Jonathan Cameron <Jonathan.Cameron@Huawei.com>,
        devicetree@vger.kernel.org, linux-iio@vger.kernel.org,
        linux-kernel@vger.kernel.org, aardelean@deviqon.com,
        Alexandru Ardelean <ardeleanalex@gmail.com>
Subject: Re: [PATCH 2/2] iio: accel: Add driver for Murata SCA3300
 accelerometer
Message-ID: <20210419204509.527570a3@jic23-huawei>
In-Reply-To: <ea58851c-3bf1-ab51-0771-6844ed53b892@vaisala.com>
References: <20210412075056.56301-1-tomas.melin@vaisala.com>
        <20210412075056.56301-3-tomas.melin@vaisala.com>
        <20210412120807.000044d3@Huawei.com>
        <87302341-f9d0-372a-1f18-b934df202e82@vaisala.com>
        <c3fca8dc-9617-220b-2085-febe2a7f3b7e@vaisala.com>
        <1541221b-3dd3-9cc6-1dfe-6a4a100579d0@vaisala.com>
        <20210418110319.72694b7e@jic23-huawei>
        <ea58851c-3bf1-ab51-0771-6844ed53b892@vaisala.com>
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On Mon, 19 Apr 2021 16:34:35 +0300
Tomas Melin <tomas.melin@vaisala.com> wrote:

> Hi,
> 
> On 4/18/21 1:03 PM, Jonathan Cameron wrote:
> > On Fri, 16 Apr 2021 15:21:14 +0300
> > Tomas Melin <tomas.melin@vaisala.com> wrote:
> >  
> >> Updated email-address for Alexandru.
> >>
> >>
> >> On 4/16/21 3:17 PM, Tomas Melin wrote:  
> >>> On 4/15/21 11:41 AM, Tomas Melin wrote:
> >>>     
> >>>> 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  
> >>>
> >>> Tested further that for this driver, loading and unloading as module
> >>> works fine until commit:
> >>>
> >>> commit f73f7f4da581875f9b1f2fb8ebd1ab15ed634488
> >>> Author: Alexandru Ardelean <alexandru.ardelean@analog.com>
> >>> Date:   Mon Feb 15 12:40:39 2021 +0200
> >>>
> >>>      iio: buffer: add ioctl() to support opening extra buffers for IIO
> >>> device
> >>>
> >>>
> >>> Any thoughts what causes this issue?  
> > Is this still happening after fixing the ordering in probe / remove?
> > (devm_iio_triggered_buffer_setup() being easiest way)
> >
> > As driver currently stands it's calling iio_triggered_buffer_cleanup
> > before the managed cleanup of the iio_device_register() call.  That
> > should never happen so would be where I'd look for problems here.
> >
> > It is possible Alex's work is relying on that ordering being correct
> > a little more than we previously were. I could be wrong though
> > and could be something else going on!
> >
> > Jonathan
> >
> > +CC Alex's other email address.  
> 
> This is still happening with v3 of driver patchset, which uses only devm_*
> 
> versions in probing. v5.12-rc7 works ok, I'm currently only seeing this 
> using linux-next.

Thanks for checking.  I've just fired up a VM and confirmed that the same
thing is happening with creating and removing instances of the dummy driver.

Will see if I can figure out what's going wrong.

Jonathan

> 
> Thanks,
> 
> Tomas
> 
> 
> >>> 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@vaisala.com>");
> >>>>>> +MODULE_DESCRIPTION("Murata SCA3300 SPI Accelerometer");
> >>>>>> +MODULE_LICENSE("GPL v2");