On Thu, Mar 17, 2016 at 11:43 AM, Gregor Boirie <gregor.boirie@xxxxxxxxxx> wrote: > Expose a rotation matrix to indicate userspace the chip placement with > respect to the overall hardware system. This is needed to adjust > coordinates sampled from a magnetometer chip when its position deviates > from the main hardware system. > > Final coordinates computation is delegated to userspace since: > * computation may involve floating point arithmetics ; > * it allows an application to combine adjustments with arbitrary > transformations. > > This 3 dimentional space rotation matrix is expressed as 3x3 array of > strings to support floating point numbers. It may be retrieved from a > "in_magn_matrix" sysfs attribute file. It is declared into ak8975 DTS > entry as a "matrix" property. Why is the sysfs interface specific to ak8975? Furthermore, why is it specific to magnetometer? Couldn't accelerometers need the same thing? There's a thread discussing a similar matrix on android-x86[1]. > diff --git a/Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt b/Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt > index 34a3206..f936f86 100644 > --- a/Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt > +++ b/Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt > @@ -9,6 +9,7 @@ Optional properties: > > - gpios : should be device tree identifier of the magnetometer DRDY pin > - vdd-supply: an optional regulator that needs to be on to provide VDD > + - matrix: an optional 3x3 mounting rotation matrix Perhaps "rotation-matrx" would be a better name in case there's ever any other matrix needed. Rob [1] https://groups.google.com/forum/#!msg/android-x86/LaKhV8cT69o/G1rrVU0_JAAJ -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
