As we intend to eventually get board related parameters from a configuration
file, this commit makes the GPIO numbers for data-ready pins be instance
variables instead of from C constant macros.
Another advantage of using instance variables in this context is the
possibility of using more than one LSM9DS0.
If the data-ready polling is done entirely on GPIO pins, it isn't necessary to
hold the semaphore before we now we have data to consume. In that case, only
take the SPI semaphore if there's new data available.
On the other hand, if at least one SPI transaction is done in order to check
for new data, then it makes sense to take the semaphore beforehand.
This commit makes accel and gyro initialization routines use bitfield macros
instead of hardcoding the literal value when wrinting on registers. That is
less prone to typos and a lot of times self-explanatory. Also, due to the
latter, the long comments explaining each register field were removed (any
detail can be checked on the datasheet).
This adds the backend driver for LSM9DS0. This implementation is based on the
legacy driver coded by Víctor Mayoral Vilches (under folder LSM9DS0) and makes
some necessary adaptations and fixes in order to work properly. The legacy
driver folder was removed.
The calibration on LSM9DS0 was giving offsets between 4.0 and 4.2 on x-axis and
around 3.6 on y-axis. It turned out that those offsets were actually right.
The maximum absolute values of calibration offset should be a sensor
characteristic rather than a constant value for all sensors.
The constant value previously used (3.5 m/s/s for all axes) is set here as a
default maximum absolute calibration offset for every instance to keep it
working.
The device number in /dev may not be reliable from one boot to another
due to the initialization order of each bus.
For example, in Minnow Board Max, the exposed I2C buses may be i2c-7 and
i2c-8 or i2c-8 and i2c-9 depending if the platform driver in the kernel
is initialized before or after the PCI.
It also may change with different version and configuration of the DT or
UEFI used making another kernel driver to bind to the device. This means that
for Minnow Board Max we need to use something like below to pass to the
constructor:
static const char * const i2c_devpaths[] = {
/* UEFI with lpss set to ACPI */
"/devices/platform/80860F41:05",
/* UEFI with lpss set to PCI */
"/devices/pci0000:00/0000:00:18.6",
NULL
};
The devpath here is the one returned by udev with the following command:
udevadm info -q path /dev/<i2c-device>
In contrary to the device number in /dev/i2c-N, this path in sysfs is
stable across reboots and can only change if there's a change in the
UEFI firmware or the board's device tree.
This patch assumes the currently supported boards don't have this
problem so it's not touching them.
Peter Barker
Andrew Tridgell
Víctor Mayoral Vilches
Gustavo Jose de Sousa
Lucas De Marchi
Michael du Breuil
mirkix
Vladislav Zakharov
Przemek Lekston
Randy Mackay
Robert Lefebvre