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Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-iio | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio index f155eff910f9..df44998e7506 100644 --- a/Documentation/ABI/testing/sysfs-bus-iio +++ b/Documentation/ABI/testing/sysfs-bus-iio @@ -1512,3 +1512,56 @@ Contact: linux-iio@vger.kernel.org Description: Raw (unscaled no offset etc.) pH reading of a substance as a negative base-10 logarithm of hydrodium ions in a litre of water. + +What: /sys/bus/iio/devices/iio:deviceX/mount_matrix +What: /sys/bus/iio/devices/iio:deviceX/in_mount_matrix +What: /sys/bus/iio/devices/iio:deviceX/out_mount_matrix +What: /sys/bus/iio/devices/iio:deviceX/in_anglvel_mount_matrix +What: /sys/bus/iio/devices/iio:deviceX/in_accel_mount_matrix +KernelVersion: 4.6 +Contact: linux-iio@vger.kernel.org +Description: + Mounting matrix for IIO sensors. This is a rotation matrix which + informs userspace about sensor chip's placement relative to the + main hardware it is mounted on. + Main hardware placement is defined according to the local + reference frame related to the physical quantity the sensor + measures. + Given that the rotation matrix is defined in a board specific + way (platform data and / or device-tree), the main hardware + reference frame definition is left to the implementor's choice + (see below for a magnetometer example). + Applications should apply this rotation matrix to samples so + that when main hardware reference frame is aligned onto local + reference frame, then sensor chip reference frame is also + perfectly aligned with it. + Matrix is a 3x3 unitary matrix and typically looks like + [0, 1, 0; 1, 0, 0; 0, 0, -1]. Identity matrix + [1, 0, 0; 0, 1, 0; 0, 0, 1] means sensor chip and main hardware + are perfectly aligned with each other. + + For example, a mounting matrix for a magnetometer sensor informs + userspace about sensor chip's ORIENTATION relative to the main + hardware. + More specifically, main hardware orientation is defined with + respect to the LOCAL EARTH GEOMAGNETIC REFERENCE FRAME where : + * Y is in the ground plane and positive towards magnetic North ; + * X is in the ground plane, perpendicular to the North axis and + positive towards the East ; + * Z is perpendicular to the ground plane and positive upwards. + + An implementor might consider that for a hand-held device, a + 'natural' orientation would be 'front facing camera at the top'. + The main hardware reference frame could then be described as : + * Y is in the plane of the screen and is positive towards the + top of the screen ; + * X is in the plane of the screen, perpendicular to Y axis, and + positive towards the right hand side of the screen ; + * Z is perpendicular to the screen plane and positive out of the + screen. + Another example for a quadrotor UAV might be : + * Y is in the plane of the propellers and positive towards the + front-view camera; + * X is in the plane of the propellers, perpendicular to Y axis, + and positive towards the starboard side of the UAV ; + * Z is perpendicular to propellers plane and positive upwards. |