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SubjectRe: [v5 00/14] Add support for Bosch BNO055 IMU
On Wed, 27 Apr 2022 15:42:49 +0200
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Tue, Apr 26, 2022 at 3:11 PM Andrea Merello <andrea.merello@gmail.com> wrote:
> >
> > From: Andrea Merello <andrea.merello@iit.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@gmail.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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