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iio:core: mounting matrix support

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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@parrot.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Gregor Boirie
2016-04-20 19:23:43 +02:00
committed by Jonathan Cameron
parent dc2c57153e
commit dfc57732ad
3 changed files with 164 additions and 0 deletions
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82
drivers/iio/industrialio-core.c
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@@ -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