Date:   Sun, 1 May 2022 18:03:03 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Andrea Merello <andrea.merello@...il.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Matt Ranostay <matt.ranostay@...sulko.com>,
        Alexandru Ardelean <ardeleanalex@...il.com>,
        jmondi <jacopo@...ndi.org>,
        Andrea Merello <andrea.merello@....it>
Subject: Re: [v5 00/14] Add support for Bosch BNO055 IMU

On Wed, 27 Apr 2022 15:42:49 +0200
Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> On Tue, Apr 26, 2022 at 3:11 PM Andrea Merello <andrea.merello@...il.com> wrote:
> >
> > From: Andrea Merello <andrea.merello@....it>
> >
> > This series (tries to) add support for Bosch BNO055 IMU to Linux IIO
> > subsystem. It is made up several patches:
> >
> >   1/14 to 6/14: add some IIO modifiers, and their documentation, to the IIO
> >                 core layer, in order to being able to expose the linear
> >                 acceleration and Euler angles among standard attributes.
> >                 Also update the IIO event monitor tool
> >
> >   7/14: fix binary attributes didn't work with IIO
> >
> >   8/14 to 11/14: add the core IIO BNO055 driver and documentation for sysfs
> >                  attributes and DT bindings
> >
> >   12/14: adds serdev BNO055 driver to actually use the IMU via serial line
> >
> >   13/14: adds I2C BNO055 driver to actually use the IMU via I2C wiring
> >
> >   14/14: add a documentation file that describe the bno055 driver and
> >          specifically the calibration  
> 
> FWIW,
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
> for non-commented patches (12 out of 14 AFAICS).
> 
FWIW I'm fine with the series once you've tidied up the stuff Andy picked up
on.

Thanks Andy for the detailed reviewing btw.

Jonathan

> > Differences wrt v4:
> > - be more tolerant wrt unrecognized chip IDs
> > - rename 'serial_number' attribute in 'serialnumber'
> > - fix missing NULL variable initialization
> > - use sign_extend32() instead of s16 casting where appropriate
> > - fix quaternion unit
> > - minor stuff (e.g. comments..)
> > - reduce (slightly) locking in serdev driver
> > - rework tracepoint support (e.g. remove dedicated config option)
> >
> > Differences wrt other BNO055 drivers:
> >
> >   Previously at least another driver for the very same chip has been posted
> >   to the Linux ML [0], but it has been never merged, and it seems no one
> >   cared of it since quite a long time.
> >
> >   This driver differs from the above driver on the following aspects:
> >
> >   - This driver supports also serial access (to be reliable, reset pin is
> >     required to be wired)
> >
> >   - The above driver tried to support all IMU HW modes by allowing to
> >     choose one in the DT, and adapting IIO attributes accordingly. This
> >     driver does not rely on DT for this, instead settings are done via
> >     sysfs attributes.  All IIO attributes are always exposed; more on this
> >     later on. This driver however supports only a subset of the
> >     HW-supported modes.
> >
> >   - This driver has some support for managing the IMU calibration
> >
> > Supported operation modes:
> >
> >   - AMG (accelerometer, magnetometer and gyroscope) mode, which provides
> >     raw (uncalibrated) measurements from the said sensors, and allows for
> >     setting some parameters about them (e.g. filter cut-off frequency, max
> >     sensor ranges, etc).
> >
> >   - Fusion mode, which still provides AMG measures, while it also provides
> >     other data calculated by the IMU (e.g. rotation angles, linear
> >     acceleration, etc). In this mode user has no freedom to set any sensor
> >     parameter, since the HW locks them. Autocalibration and correction is
> >     performed by the IMU.
> >
> >   IIO attributes exposing sensors parameters are always present, but in
> >   fusion modes the available values are constrained to just the one used by
> >   the HW. This is reflected in the '*_available' IIO attributes.
> >
> >   Trying to set a not-supported value always falls back to the closest
> >   supported one, which in this case is just the one in use by the HW.
> >
> >   IIO attributes for unavailable measurements (e.g. Euler angles in AMG
> >   mode) can't be read (return -EBUSY, or refuse to enable buffer).
> >
> > IMU calibration:
> >
> >   The IMU supports for two sets of calibration parameters:
> >
> >   - SIC matrix. user-provided; this driver doesn't currently support it
> >
> >   - Offset and radius parameters. The IMU automatically finds out them when
> >     it is running in fusion mode; supported by this driver.
> >
> >   The driver provides access to autocalibration flags (i.e. you can known
> >   if the IMU has successfully autocalibrated) and to calibration data blob.
> >   The user can save this blob in a "firmware" file (i.e. in /lib/firmware)
> >   that the driver looks for at probe time. If found, then the IMU is
> >   initialized with this calibration data. This saves the user from
> >   performing the calibration procedure every time (which consist of moving
> >   the IMU in various way).
> >
> >   The driver looks for calibration data file using two different names:
> >   first a file whose name is suffixed with the IMU unique ID is searched
> >   for; this is useful when there is more than one IMU instance. If this
> >   file is not found, then a "generic" calibration file is searched for
> >   (which can be used when only one IMU is present, without struggling with
> >   fancy names, that changes on each device).
> >
> >   In AMG mode the IIO 'offset' attributes provide access to the offsets
> >   from calibration data (if any), so that the user can apply them to the
> >   accel, angvel and magn IIO attributes. In fusion mode they are not needed
> >   and read as zero.
> >
> >
> > Access protocols and serdev module:
> >
> >   The serial protocol is quite simple, but there are tricks to make it
> >   really works. Those tricks and workarounds are documented in the driver
> >   source file.
> >
> >   The core BNO055 driver tries to group readings in burst when appropriate,
> >   in order to optimize triggered buffer operation. The threshold for
> >   splitting a burst (i.e. max number of unused bytes in the middle of a
> >   burst that will be throw away) is provided to the core driver by the
> >   lowlevel access driver (either serdev or I2C) at probe time.
> >
> > [0] https://www.spinics.net/lists/linux-iio/msg25508.html
> >
> > Andrea Merello (14):
> >   iio: add modifiers for linear acceleration
> >   iio: document linear acceleration modifiers
> >   iio: event_monitor: add linear acceleration modifiers
> >   iio: add modifers for pitch, yaw, roll
> >   iio: document pitch, yaw, roll modifiers
> >   iio: event_monitor: add pitch, yaw and roll modifiers
> >   iio: add support for binary attributes
> >   iio: imu: add Bosch Sensortec BNO055 core driver
> >   iio: document bno055 private sysfs attributes
> >   iio: document "serialnumber" sysfs attribute
> >   dt-bindings: iio/imu: Add Bosch BNO055
> >   iio: imu: add BNO055 serdev driver
> >   iio: imu: add BNO055 I2C driver
> >   docs: iio: add documentation for BNO055 driver
> >
> >  Documentation/ABI/testing/sysfs-bus-iio       |   25 +
> >  .../ABI/testing/sysfs-bus-iio-bno055          |   81 +
> >  .../bindings/iio/imu/bosch,bno055.yaml        |   59 +
> >  Documentation/iio/bno055.rst                  |   50 +
> >  Documentation/iio/index.rst                   |    2 +
> >  drivers/iio/imu/Kconfig                       |    1 +
> >  drivers/iio/imu/Makefile                      |    1 +
> >  drivers/iio/imu/bno055/Kconfig                |   25 +
> >  drivers/iio/imu/bno055/Makefile               |   10 +
> >  drivers/iio/imu/bno055/bno055.c               | 1710 +++++++++++++++++
> >  drivers/iio/imu/bno055/bno055.h               |   12 +
> >  drivers/iio/imu/bno055/bno055_i2c.c           |   57 +
> >  drivers/iio/imu/bno055/bno055_ser_core.c      |  560 ++++++
> >  drivers/iio/imu/bno055/bno055_ser_trace.h     |  104 +
> >  drivers/iio/industrialio-core.c               |   10 +-
> >  include/uapi/linux/iio/types.h                |    7 +-
> >  tools/iio/iio_event_monitor.c                 |    6 +
> >  17 files changed, 2718 insertions(+), 2 deletions(-)
> >  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-bno055
> >  create mode 100644 Documentation/devicetree/bindings/iio/imu/bosch,bno055.yaml
> >  create mode 100644 Documentation/iio/bno055.rst
> >  create mode 100644 drivers/iio/imu/bno055/Kconfig
> >  create mode 100644 drivers/iio/imu/bno055/Makefile
> >  create mode 100644 drivers/iio/imu/bno055/bno055.c
> >  create mode 100644 drivers/iio/imu/bno055/bno055.h
> >  create mode 100644 drivers/iio/imu/bno055/bno055_i2c.c
> >  create mode 100644 drivers/iio/imu/bno055/bno055_ser_core.c
> >  create mode 100644 drivers/iio/imu/bno055/bno055_ser_trace.h
> >
> > --
> > 2.17.1  
> 
> 
> 

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