On 20/04/16 18:23, Gregor Boirie 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 sensor 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
> "[<dir>_][<type>_]mount_matrix" sysfs attribute file. It is declared into a
> device / driver specific DTS property or platform data.
>
> Signed-off-by: Gregor Boirie <gregor.boirie@xxxxxxxxxx>
Applied to the togreg branch of iio.git - initially pushed out as testing
for the autobuilders to play with it.
Thanks,
Jonathan
> ---
> Documentation/ABI/testing/sysfs-bus-iio | 51 ++++++++++++++++++++
> drivers/iio/industrialio-core.c | 82 +++++++++++++++++++++++++++++++++
> include/linux/iio/iio.h | 31 +++++++++++++
> 3 files changed, 164 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index f155eff..ba8df69 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -1512,3 +1512,54 @@ Contact: linux-iio@xxxxxxxxxxxxxxx
> 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
> +KernelVersion: 4.6
> +Contact: linux-iio@xxxxxxxxxxxxxxx
> +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.
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 190a593..e6319a9 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -412,6 +412,88 @@ ssize_t iio_enum_write(struct iio_dev *indio_dev,
> }
> EXPORT_SYMBOL_GPL(iio_enum_write);
>
> +static const struct iio_mount_matrix iio_mount_idmatrix = {
> + .rotation = {
> + "1", "0", "0",
> + "0", "1", "0",
> + "0", "0", "1"
> + }
> +};
> +
> +static int iio_setup_mount_idmatrix(const struct device *dev,
> + struct iio_mount_matrix *matrix)
> +{
> + *matrix = iio_mount_idmatrix;
> + dev_info(dev, "mounting matrix not found: using identity...\n");
> + return 0;
> +}
> +
> +ssize_t iio_show_mount_matrix(struct iio_dev *indio_dev, uintptr_t priv,
> + const struct iio_chan_spec *chan, char *buf)
> +{
> + const struct iio_mount_matrix *mtx = ((iio_get_mount_matrix_t *)
> + priv)(indio_dev, chan);
> +
> + if (IS_ERR(mtx))
> + return PTR_ERR(mtx);
> +
> + if (!mtx)
> + mtx = &iio_mount_idmatrix;
> +
> + return snprintf(buf, PAGE_SIZE, "%s, %s, %s; %s, %s, %s; %s, %s, %s\n",
> + mtx->rotation[0], mtx->rotation[1], mtx->rotation[2],
> + mtx->rotation[3], mtx->rotation[4], mtx->rotation[5],
> + mtx->rotation[6], mtx->rotation[7], mtx->rotation[8]);
> +}
> +EXPORT_SYMBOL_GPL(iio_show_mount_matrix);
> +
> +/**
> + * of_iio_read_mount_matrix() - retrieve iio device mounting matrix from
> + * device-tree "mount-matrix" property
> + * @dev: device the mounting matrix property is assigned to
> + * @propname: device specific mounting matrix property name
> + * @matrix: where to store retrieved matrix
> + *
> + * If device is assigned no mounting matrix property, a default 3x3 identity
> + * matrix will be filled in.
> + *
> + * Return: 0 if success, or a negative error code on failure.
> + */
> +#ifdef CONFIG_OF
> +int of_iio_read_mount_matrix(const struct device *dev,
> + const char *propname,
> + struct iio_mount_matrix *matrix)
> +{
> + if (dev->of_node) {
> + int err = of_property_read_string_array(dev->of_node,
> + propname, matrix->rotation,
> + ARRAY_SIZE(iio_mount_idmatrix.rotation));
> +
> + if (err == ARRAY_SIZE(iio_mount_idmatrix.rotation))
> + return 0;
> +
> + if (err >= 0)
> + /* Invalid number of matrix entries. */
> + return -EINVAL;
> +
> + if (err != -EINVAL)
> + /* Invalid matrix declaration format. */
> + return err;
> + }
> +
> + /* Matrix was not declared at all: fallback to identity. */
> + return iio_setup_mount_idmatrix(dev, matrix);
> +}
> +#else
> +int of_iio_read_mount_matrix(const struct device *dev,
> + const char *propname,
> + struct iio_mount_matrix *matrix)
> +{
> + return iio_setup_mount_idmatrix(dev, matrix);
> +}
> +#endif
> +EXPORT_SYMBOL(of_iio_read_mount_matrix);
> +
> /**
> * iio_format_value() - Formats a IIO value into its string representation
> * @buf: The buffer to which the formatted value gets written
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index 0b2773a..7c29cb0 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -148,6 +148,37 @@ ssize_t iio_enum_write(struct iio_dev *indio_dev,
> }
>
> /**
> + * struct iio_mount_matrix - iio mounting matrix
> + * @rotation: 3 dimensional space rotation matrix defining sensor alignment with
> + * main hardware
> + */
> +struct iio_mount_matrix {
> + const char *rotation[9];
> +};
> +
> +ssize_t iio_show_mount_matrix(struct iio_dev *indio_dev, uintptr_t priv,
> + const struct iio_chan_spec *chan, char *buf);
> +int of_iio_read_mount_matrix(const struct device *dev, const char *propname,
> + struct iio_mount_matrix *matrix);
> +
> +typedef const struct iio_mount_matrix *
> + (iio_get_mount_matrix_t)(const struct iio_dev *indio_dev,
> + const struct iio_chan_spec *chan);
> +
> +/**
> + * IIO_MOUNT_MATRIX() - Initialize mount matrix extended channel attribute
> + * @_shared: Whether the attribute is shared between all channels
> + * @_get: Pointer to an iio_get_mount_matrix_t accessor
> + */
> +#define IIO_MOUNT_MATRIX(_shared, _get) \
> +{ \
> + .name = "mount_matrix", \
> + .shared = (_shared), \
> + .read = iio_show_mount_matrix, \
> + .private = (uintptr_t)(_get), \
> +}
> +
> +/**
> * struct iio_event_spec - specification for a channel event
> * @type: Type of the event
> * @dir: Direction of the event
>
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