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SubjectRe: [v5 00/14] Add support for Bosch BNO055 IMU
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).

> 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



--
With Best Regards,
Andy Shevchenko

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